This document summarizes a study on using liquid desiccants to improve energy efficiency in air conditioning. It discusses how liquid desiccants can remove moisture from air more efficiently than vapor compression alone, avoiding the need for overcooling and reheating. The document describes low-flow liquid desiccant air conditioning technology, how it works in a conditioner and regenerator, and its potential benefits, such as reduced energy consumption and improved indoor air quality. Key findings include that mass transfer coefficients and energy savings increase significantly with higher humidity ratios, while Lewis numbers decrease more slowly with increased desiccant concentration.
THERMAL INVESTIGATION ON OPEN CYCLE DESICCANT COOLING AIR CONDITIONINGIjripublishers Ijri
In hot and humid countries like India, Air-conditioning systems of solid desiccant dehumidification based on direct
evaporative cooling can be an effective alternative to the existing vapor compression refrigeration air conditioning due
to its various advantages in, decreasing latent load of air, environmentally friendly, no pollutants in the process air,
decreeing power utilization and finally the equipment cost is much lower. This project first deeply explains about recent
researches and developments in solid desiccant dehumidification combined with direct evaporative cooling technologies.
A basic description of the principle operation for solid desiccants and different types of desiccant materials is given first.
Next, solid desiccant dehumidification system design and working process is included.
Enhancement of the processes of desiccant aireSAT Journals
Abstract An experimental study was carried out to evaluate the liquid desiccant system performance during dehumidification and humidification processes using air injection through the liquid desiccant solution (Calcium Chloride). The air flows cross the desiccant solution with different air mass flow rates. The system is studied at different operating condition (air flow rate, temperature, humidity ratio and solution levels). The effectiveness of the proposed system for both dehumidification and humidification processes were evaluated. Also, the cooling effect and mass transfer coefficient was obtained. It is found that the system effectiveness reached 0.75 in the dehumidification process and 0.7 in the humidification process. Mass transfer coefficient depends on the air mass flow rate and the desiccant solution level in the tank Economical Results of the presented system is estimated Keywords : Air humidification , Air dehumdificaion, Liquid Desiccant
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
A Systemic Optimization Approach for the Design of Natural Gas Dehydration PlantIJRES Journal
In designing dehydration units for natural gas, several critical parameters exist which can be varied to achieve a specified dew point depression. This paper studies the effects of varying number of trays in the contactor, glycol circulation rate through the contactor, temperature of the reboiler in the regenerator, amount of stripping gas used and operating pressure of the regenerator on the water content of the gas in a glycol dehydration unit. The effect of incorporating free water knock out (FWKO) tank before the absorber is also presented. An offshore platform in the Arctic region was chosen as the base case of this simulation and was modeled by using ASPEN HYSYS. Results show that the incorporation of FWKOT does not affect the TEG circulation rate required to approach equilibrium.
THE ROLE OF CONDUCTIVE PACKING IN DIRECT CONTACT HUMIDIFICATION-DEHUMIDIFICAT...IAEME Publication
In solar desalination by humidification-dehumidification (HDH) technique, heating the air prior to entering a humidifier enhances the production of fresh water. This phenomenon can be used to increase the system’s productivity in a multiple effect heating humidification (MEHH) process. In this study, spherical conductive packing elements to enhance the evaporation and condensation rates have been applied to achieve the MEHH as well as multiple effects of cooling /dehumidification (MECD) while air passes through the successive packing layers in the evaporator and condenser
respectively.
THERMAL INVESTIGATION ON OPEN CYCLE DESICCANT COOLING AIR CONDITIONINGIjripublishers Ijri
In hot and humid countries like India, Air-conditioning systems of solid desiccant dehumidification based on direct
evaporative cooling can be an effective alternative to the existing vapor compression refrigeration air conditioning due
to its various advantages in, decreasing latent load of air, environmentally friendly, no pollutants in the process air,
decreeing power utilization and finally the equipment cost is much lower. This project first deeply explains about recent
researches and developments in solid desiccant dehumidification combined with direct evaporative cooling technologies.
A basic description of the principle operation for solid desiccants and different types of desiccant materials is given first.
Next, solid desiccant dehumidification system design and working process is included.
Enhancement of the processes of desiccant aireSAT Journals
Abstract An experimental study was carried out to evaluate the liquid desiccant system performance during dehumidification and humidification processes using air injection through the liquid desiccant solution (Calcium Chloride). The air flows cross the desiccant solution with different air mass flow rates. The system is studied at different operating condition (air flow rate, temperature, humidity ratio and solution levels). The effectiveness of the proposed system for both dehumidification and humidification processes were evaluated. Also, the cooling effect and mass transfer coefficient was obtained. It is found that the system effectiveness reached 0.75 in the dehumidification process and 0.7 in the humidification process. Mass transfer coefficient depends on the air mass flow rate and the desiccant solution level in the tank Economical Results of the presented system is estimated Keywords : Air humidification , Air dehumdificaion, Liquid Desiccant
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
A Systemic Optimization Approach for the Design of Natural Gas Dehydration PlantIJRES Journal
In designing dehydration units for natural gas, several critical parameters exist which can be varied to achieve a specified dew point depression. This paper studies the effects of varying number of trays in the contactor, glycol circulation rate through the contactor, temperature of the reboiler in the regenerator, amount of stripping gas used and operating pressure of the regenerator on the water content of the gas in a glycol dehydration unit. The effect of incorporating free water knock out (FWKO) tank before the absorber is also presented. An offshore platform in the Arctic region was chosen as the base case of this simulation and was modeled by using ASPEN HYSYS. Results show that the incorporation of FWKOT does not affect the TEG circulation rate required to approach equilibrium.
THE ROLE OF CONDUCTIVE PACKING IN DIRECT CONTACT HUMIDIFICATION-DEHUMIDIFICAT...IAEME Publication
In solar desalination by humidification-dehumidification (HDH) technique, heating the air prior to entering a humidifier enhances the production of fresh water. This phenomenon can be used to increase the system’s productivity in a multiple effect heating humidification (MEHH) process. In this study, spherical conductive packing elements to enhance the evaporation and condensation rates have been applied to achieve the MEHH as well as multiple effects of cooling /dehumidification (MECD) while air passes through the successive packing layers in the evaporator and condenser
respectively.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Experimental Investigation of Water Cooler Test Rig Using R-22 as RefrigerantIJMERJOURNAL
ABSTRACT: This paper describes Water Cooler; a tool that aggregates shared internal social media and cross-references it with an organization’s directory. We deployed Water Cooler in a large global enterprise and present the results of a preliminary user study. Despite the lack of complete social networking affordances, we find that Water-Cooler changed users’ perceptions of their workplace, made them feel more connected to each other and the company, and redistributed. Water coolers work on vapour compression refrigeration cycle. The behavior of performance parameters of a simple vapour compression refrigeration system were studied while it’s working under transient conditions occurred during cooling of a fixed mass of brine from initial room temperature to sub-zero refrigeration temperature. The effects of different lengths of capillary tube over these characteristics have also been investigated. The main advantage of our project is to cool the water with help of test rig.
Emerson climate technologies 2010 - Refrigerant choices for commercial refrig...Jesús Catalán Gil
Emerson Climate Technologies is committed to supporting solutions that safeguard food and protect
the environment. Minimising the impact of climate change through responsible energy use and reducing
carbon footprint are key environmental objectives.
This study is designed to help our customers meet these objectives by providing guidance to the complex
decision-making process when specifying supermarket cabinet cooling systems, both for new build and
major refurbishment projects. It focuses on the refrigerant but takes into account the refrigeration system
architecture and technology which have an impact on energy consumption, environment and investment
costs. Supermarkets were chosen in this study as they offer the greatest potential to integrate the latest
refrigeration design principles in order to improve environmental performance.
Fourteen combinations of system technologies and refrigerants are investigated and referred to as “cases”.
The study sets out the refrigerant, compressor technology, and system type for each case, together with
alternatives and the operating conditions associated with them.
We have started from a baseline with a reference supermarket containing a sales area of 1000-1200m2,
typical of the store formats found throughout Europe. This Case 1 supermarket establishes the base with
which different refrigerant / technology combinations are compared.
The study includes five refrigerant / technology combinations for supermarket refrigeration systems -
centralised Direct Expansion (DX), distributed Direct Expansion, cascade system, secondary system, and
R744 booster transcritical system.
Effect of Solar Daylighting on Indoor Visual Environment for an Office Spaceiskandaruz
Hyunjoo Han, Saffa B. Riffat
Institute of Sustainable Energy Technology, School of the Built Environment, University of Nottingham
University Park, NG7 2RD, United Kingdom
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
An Investigative and Concise Review on Evaporation and Condensation Processes...IJERA Editor
The vapour adsorption refrigeration is based on the evaporation and condensation of a refrigerant combined with adsorption or chemical reaction. The towering fossil fuel price and the responsiveness of environmental problems offer many potential applications to thermal powered adsorption cooling. However, the adsorption cooling machines still have some disadvantages that hinder their wide application. The patents surveyed are classified into four main groups: adsorption system development, adsorbent bed innovation, adsorbent/adsorbate material development and novel application of adsorption cooling system. The adsorption refrigeration is based on the evaporation and condensation of a refrigerant combined with adsorption or chemical reaction. Important targets are to reach a high efficiency through optimization measures at various components and the control system. On the other hand measures are to verify to simplify the construction with regard to a low-cost manufacturing, as well as to reach long periods with maintenance-free operation. This review paper gives a comprehensive review on the work carried out on vapour adsorption refrigeration for cryogenic applications.
An Experimental Evaluation of Energy Saving in a Split-type Air Conditioner w...drboon
This research aims to experimentally evaluate the energy saving in a split-type air conditioner, which is using various types of evaporative cooling systems. The condensing unit is retrofitted with a cellulose corrugated pad, water sprayers, a water source and a pump. The power consumption and refrigeration capacity obtained from various cooling types are monitored and compared. The results show that the electrical consumption and coefficient of performance (COPR) significantly depend on the ambient conditions. Due to effects of condensing pressure, when the ambient temperature rises, the electrical consumption becomes higher, while the COPR becomes lower. Utilizing the indirect evaporative cooling system decreases the temperature of air entering the condensing unit, and this causes the system performance to be enhanced considerably. Among the investigated cases, the maximum energy saving occurs when the water spray cooperates with cellulose cooling pad. By using the evaporative cooling systems, COPR is improved by around 6-48%, and electrical consumption is approximately reduced by 4-15%.
Numerical and Experimental Investigation Plane Fin with the Help of Passive A...iosrjce
As we know that fins are basically a extended surface which is use to increase the heat transfer rate,
this is basically a secondary surface mounted on primary surface to augment heat transfer from it . To dissipate
heat at faster rate, different heat transfer enhancement methods have been suggested in literature. Active and
passive heat transfer techniques are commonly employed for heat transfer augmentation in fluids.
Recent development in technology has led to demand for high performance lightweight, and compact heat
transfer equipment. To provide accommodation with this demand, finned surface are usually used to increase
rate of heat transfer. The excessive heat must be dissipated to the surrounding for smooth functioning of system.
This is more important in cooling of gas turbine blade, thermal power plants, air conditioning equipment and
electrical / electronic component. This component is getting more compacting size, which generates heat
continuously. This excessive heat will reduce the life of component. To overcome this problem there is need of
effective cooling system. Therefore now a day’s industries are utilizing thermal system such as ribs, fins, baffles
etc. The turbulence occurred due to these passive techniques are good enough to increase rate of heat transfer.
Our project is an extension in this direction to analysis the heat augmentation capacity of rectangular heat fin
array.
Statistical Optimization of process parameters for SiO2-Nickel nanocomposites...IJERA Editor
The optimum combination of process parameters - temperature, time of reduction under nitrogen atmosphere and amount of NiCl2 was delineated to find the maximum yield of nanocrystallite Ni in the synthesized silica gel matrix. A statistically adequate regression equation, within 95% confidence limit was developed by carrying out a set of experiments within the framework of design of experiment. The regression equation is found to indicate the beneficial role of the temperature and time of reduction.
Cloud Trust Management Framework Based On Cloud Market spacesIJERA Editor
Nowadays, applications running in virtual or cloud-based environments are all susceptible to exploitation. However, traditional trust solutions have not been fully optimized for virtualized third party environments. In this situation, the selection of an appropriate cloud service provider is an issue. This paper introduces a completely novel idea on most appropriate cloud service selection through an intermediator. It is based on the new notion of a marketspace. Our paper is devoted to the investigation of a novel architecture suggested for a marketspace. Several theoretical notions related to trust have also been explained extensively in the paper for Cloud service provider selection.
Optimization of Metal Removal Rateon Cylindrical Grinding For Is 319 Brass Us...IJERA Editor
Cylindrical grinding is one of the most important metal cutting processes used extensively in the Metal finishing operations. Metal removal rate and surface finish are the important output responses in the production with respect to quantity and quality respectively. The objective of this paper is to arrive at the optimal grinding conditions that will maximize metal removal rate when grinding IS 319 brass. Empirical models were developed using design of experiments by Taguchi L9 Orthogonal Array and the adequacy of the developed model is tested with ANOVA.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Experimental Investigation of Water Cooler Test Rig Using R-22 as RefrigerantIJMERJOURNAL
ABSTRACT: This paper describes Water Cooler; a tool that aggregates shared internal social media and cross-references it with an organization’s directory. We deployed Water Cooler in a large global enterprise and present the results of a preliminary user study. Despite the lack of complete social networking affordances, we find that Water-Cooler changed users’ perceptions of their workplace, made them feel more connected to each other and the company, and redistributed. Water coolers work on vapour compression refrigeration cycle. The behavior of performance parameters of a simple vapour compression refrigeration system were studied while it’s working under transient conditions occurred during cooling of a fixed mass of brine from initial room temperature to sub-zero refrigeration temperature. The effects of different lengths of capillary tube over these characteristics have also been investigated. The main advantage of our project is to cool the water with help of test rig.
Emerson climate technologies 2010 - Refrigerant choices for commercial refrig...Jesús Catalán Gil
Emerson Climate Technologies is committed to supporting solutions that safeguard food and protect
the environment. Minimising the impact of climate change through responsible energy use and reducing
carbon footprint are key environmental objectives.
This study is designed to help our customers meet these objectives by providing guidance to the complex
decision-making process when specifying supermarket cabinet cooling systems, both for new build and
major refurbishment projects. It focuses on the refrigerant but takes into account the refrigeration system
architecture and technology which have an impact on energy consumption, environment and investment
costs. Supermarkets were chosen in this study as they offer the greatest potential to integrate the latest
refrigeration design principles in order to improve environmental performance.
Fourteen combinations of system technologies and refrigerants are investigated and referred to as “cases”.
The study sets out the refrigerant, compressor technology, and system type for each case, together with
alternatives and the operating conditions associated with them.
We have started from a baseline with a reference supermarket containing a sales area of 1000-1200m2,
typical of the store formats found throughout Europe. This Case 1 supermarket establishes the base with
which different refrigerant / technology combinations are compared.
The study includes five refrigerant / technology combinations for supermarket refrigeration systems -
centralised Direct Expansion (DX), distributed Direct Expansion, cascade system, secondary system, and
R744 booster transcritical system.
Effect of Solar Daylighting on Indoor Visual Environment for an Office Spaceiskandaruz
Hyunjoo Han, Saffa B. Riffat
Institute of Sustainable Energy Technology, School of the Built Environment, University of Nottingham
University Park, NG7 2RD, United Kingdom
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
An Investigative and Concise Review on Evaporation and Condensation Processes...IJERA Editor
The vapour adsorption refrigeration is based on the evaporation and condensation of a refrigerant combined with adsorption or chemical reaction. The towering fossil fuel price and the responsiveness of environmental problems offer many potential applications to thermal powered adsorption cooling. However, the adsorption cooling machines still have some disadvantages that hinder their wide application. The patents surveyed are classified into four main groups: adsorption system development, adsorbent bed innovation, adsorbent/adsorbate material development and novel application of adsorption cooling system. The adsorption refrigeration is based on the evaporation and condensation of a refrigerant combined with adsorption or chemical reaction. Important targets are to reach a high efficiency through optimization measures at various components and the control system. On the other hand measures are to verify to simplify the construction with regard to a low-cost manufacturing, as well as to reach long periods with maintenance-free operation. This review paper gives a comprehensive review on the work carried out on vapour adsorption refrigeration for cryogenic applications.
An Experimental Evaluation of Energy Saving in a Split-type Air Conditioner w...drboon
This research aims to experimentally evaluate the energy saving in a split-type air conditioner, which is using various types of evaporative cooling systems. The condensing unit is retrofitted with a cellulose corrugated pad, water sprayers, a water source and a pump. The power consumption and refrigeration capacity obtained from various cooling types are monitored and compared. The results show that the electrical consumption and coefficient of performance (COPR) significantly depend on the ambient conditions. Due to effects of condensing pressure, when the ambient temperature rises, the electrical consumption becomes higher, while the COPR becomes lower. Utilizing the indirect evaporative cooling system decreases the temperature of air entering the condensing unit, and this causes the system performance to be enhanced considerably. Among the investigated cases, the maximum energy saving occurs when the water spray cooperates with cellulose cooling pad. By using the evaporative cooling systems, COPR is improved by around 6-48%, and electrical consumption is approximately reduced by 4-15%.
Numerical and Experimental Investigation Plane Fin with the Help of Passive A...iosrjce
As we know that fins are basically a extended surface which is use to increase the heat transfer rate,
this is basically a secondary surface mounted on primary surface to augment heat transfer from it . To dissipate
heat at faster rate, different heat transfer enhancement methods have been suggested in literature. Active and
passive heat transfer techniques are commonly employed for heat transfer augmentation in fluids.
Recent development in technology has led to demand for high performance lightweight, and compact heat
transfer equipment. To provide accommodation with this demand, finned surface are usually used to increase
rate of heat transfer. The excessive heat must be dissipated to the surrounding for smooth functioning of system.
This is more important in cooling of gas turbine blade, thermal power plants, air conditioning equipment and
electrical / electronic component. This component is getting more compacting size, which generates heat
continuously. This excessive heat will reduce the life of component. To overcome this problem there is need of
effective cooling system. Therefore now a day’s industries are utilizing thermal system such as ribs, fins, baffles
etc. The turbulence occurred due to these passive techniques are good enough to increase rate of heat transfer.
Our project is an extension in this direction to analysis the heat augmentation capacity of rectangular heat fin
array.
Statistical Optimization of process parameters for SiO2-Nickel nanocomposites...IJERA Editor
The optimum combination of process parameters - temperature, time of reduction under nitrogen atmosphere and amount of NiCl2 was delineated to find the maximum yield of nanocrystallite Ni in the synthesized silica gel matrix. A statistically adequate regression equation, within 95% confidence limit was developed by carrying out a set of experiments within the framework of design of experiment. The regression equation is found to indicate the beneficial role of the temperature and time of reduction.
Cloud Trust Management Framework Based On Cloud Market spacesIJERA Editor
Nowadays, applications running in virtual or cloud-based environments are all susceptible to exploitation. However, traditional trust solutions have not been fully optimized for virtualized third party environments. In this situation, the selection of an appropriate cloud service provider is an issue. This paper introduces a completely novel idea on most appropriate cloud service selection through an intermediator. It is based on the new notion of a marketspace. Our paper is devoted to the investigation of a novel architecture suggested for a marketspace. Several theoretical notions related to trust have also been explained extensively in the paper for Cloud service provider selection.
Optimization of Metal Removal Rateon Cylindrical Grinding For Is 319 Brass Us...IJERA Editor
Cylindrical grinding is one of the most important metal cutting processes used extensively in the Metal finishing operations. Metal removal rate and surface finish are the important output responses in the production with respect to quantity and quality respectively. The objective of this paper is to arrive at the optimal grinding conditions that will maximize metal removal rate when grinding IS 319 brass. Empirical models were developed using design of experiments by Taguchi L9 Orthogonal Array and the adequacy of the developed model is tested with ANOVA.
All people want to improve their quality of life and this can be achieved only by technology. Many problems are faced by daily vehicle users in payment based parking systems, both in open air parking system where the parking is done along the streets and in closed parking system where parking is done in closed infrastructure added with entry and exit points. Delays (long queues) and accuracy in fares are the main problems faced by the users. Many solutions are proposed to solve this problem but all have their own drawbacks. In this paper a new solution is proposed based on Near Field Communication (NFC) which makes the payment system reliable and easy.
Evolving Swings (topics) from Social Streams using Probability ModelIJERA Editor
Evolving swings from social streams is receiving renewed interest and it is motivated by the growth of social
media and social streams. Non-conventional based approaches can be appropriate which include text, images,
URLs and videos. The focus is on evolving topics by social aspects of the networks and the mentions of user
links between users which are generated intentionally or unintentionally through replies, mentions and retweets.
A probability model of the mentioning behavior is proposed and the proposed model detects the evolving topic
from the anomalies measured. After a several experiments, it shows that mention anomaly based approaches
detects the evolving swing as early as text anomaly based approa0ches.
Preparation and Characterization of Lithium Ion Conducting Solid Polymer Elec...IJERA Editor
Solid Polymer electrolyte films have been prepared from Starch-Poly vinyl alcohol (PVA) blend a well acknowledged biodegradable material. Solution cast technique was employed for the preparation of solid polymer electrolyte films added with Lithium Bromide (LiBr) salt. X-ray diffraction (XRD) studies of the prepared films portrayed the evolution of an amorphous structure with increasing content of salt which is an important factor that leads to the augmentation of conductivity. Electrochemical impedance spectroscopic analysis revealed noticeable ionic conductivity ~ 5x 10-3 S/cm for 20 wt% of salt at ambient conditions. Ionic conductivity showed an increasing trend with salt content at ambient conditions. Transference number measurements confirmed the ionic nature of the prepared solid polymer electrolyte films. Dielectric studies revealed a sharp increase in the number of charge carriers which contributed to enhancement in conductivity. Low values of activation energy extracted from temperature dependent conductivity measurements could be favorable for device applications. For the composition with highest conductivity a temperature independent relaxation mechanism was confirmed by electric modulus scaling.
Parametric Study of Multi-Spot Welded Lap Shear Specimen for Shear StrengthIJERA Editor
The effect of number of spots, spot spacing, squeezing force, welding current, weld time , overlapping length
and sheet thicknesson the shear strength of two similar galvanized steel sheets are investigated through
experiments using RSM method. Similar sheets of galvanized steel sheets are made by resistance spot welding
at different processing conditions and these joint populations were tested under lap-shear loading conditions.
Specially fabricated fixture is used to load the lap shear specimen in the universal testing machine Regression
analysis is done to obtain relationship between shear strength and selected parameters. The experimental results
indicate that the failure loads of spot welds in lap-shear specimens increase when number of spot, squeezing
force, welding current and sheet thickness increase for the given ranges.
Design and Implementation of Multibit Flip flops by Using Single Phase Adiaba...IJERA Editor
As technology advances, a system on chip (SOC) design can contain more and more components that lead to a
high power density. Now-a-days in IC's, the power consumed by clocking gradually takes a dominant part. .
Power, Area, Performance has become a main issue in VLSI design. In previous designs they have performed a
co-ordinate transformation to identify the flip-flops that can be merged and their legal regions. A combinational
table is formed by that flip-flops. Finally they used hierarchical way to merge the flip-flops. Due to this design
the power consumption can be reduced by replacing some flip-flops by fewer multi-bit flip-flops. We have
proposed an single phase adiabatic clock in for further reduction of the power. In our design also first we will
identify the mergeable flip-flops, build a combinational table from mergeable flip-flops and all the flip-flops are
divided into sub regions to check whether they are working properly or not and finally these flip-flops are
combined together, at this point we are giving an single phase adiabatic clock as input to those flip-flops for the
reduction of power consumption and timing.
Application of Elastic Layered System in the Design of RoadIJERA Editor
Elastic layered system is widely used in road design because of its reasonable assumptions, simple calculation model and typical represent activeness. Although the hypothesis is partly different from the actual structure, it is irreplaceable and worthy of further study in the current level of science and technology. This paper lists and briefly describes the application of elastic layered system theory in the calculation of asphalt pavement thickness and subgrade the stress analysis of cement concrete pavement and porous concrete base load to illustrate the generalizability of application of elastic layered system and look to the future road.
Image Restoration UsingNonlocally Centralized Sparse Representation and histo...IJERA Editor
Due to the degradation of observed image the noisy, blurred, distorted image can be occurred .To restore the image informationby conventional modelsmay not be accurate enough for faithful reconstruction of the original image. I propose the sparse representations to improve the performance of based image restoration. In this method the sparse coding noise is added for image restoration, due to this image restoration the sparse coefficients of original image can be detected. The so-called nonlocally centralized sparse representation (NCSR) model is as simple as the standard sparse representation model, fordenoising the image here we use the histogram clipping method by using histogram based sparse representation to effectively reduce the noise and also implement the TMR filter for Quality image. Various types of image restoration problems, including denoising, deblurring and super-resolution, validate the generality and state-of-the-art performance of the proposed algorithm.
Electroelastic Response of a Piezoelectric Semi-infinite Body with D∞ Symmetr...IJERA Editor
In this paper, with the aim of developing a nondestructive evaluation technique using piezoelectric signals in
wooden materials, we theoretically study the electroelastic field in a semi-infinite body with D∞ symmetry
subjected to surface friction parallel to the ∞-fold rotation axis. By applying the analytical technique previously
proposed by us, we formulate expressions for electroelastic field quantities, including electric potential, electric
field, electric displacement, elastic displacement, strain, and stress by using two “elastic displacement potential
functions” and two “piezoelastic displacement potential functions.” These potential functions and, consequently,
the electroelastic field quantities are formulated using Fourier transforms in order to satisfy electroelastic
boundary conditions. We carried out numerical calculations to correctly evaluate field quantities inside the body
and at its surface. As a result, we were successful in quantitatively elucidating the surface electric displacement
in response to the elastic stimulus of surface friction and suggested the possibility of a nondestructive evaluation
technique using piezoelectric signals.
Synthesis of Calcium Silicate (Casio3) Using Calcium Fluoride, Quartz and Mic...IJERA Editor
Microbes like bacteria, algae, fungi and virus play an important role to catalyst chemical reactions. In Nature,
ores or minerals of different compounds are formed due to microbial environment and other factors like
weathering. Microbial environment is also instrumental in forming calcium containing silicate minerals.
Chemical reactions occur under microbial environment because microbes have the ability to control or modify
different factors like pH, chemical potential and temperature during reactions. In this paper, synthesis of calcium
silicate (CaSiO3) using calcium fluoride (CaF2) and quartz (SiO2) under microbial environment in a laboratory is
being adopted to produce the required material. XRD technique is used to confirm the formation of CaSiO3.
Dual-Level Adaptive Supply Voltage System with Bandgap Reference MPR for Vari...IJERA Editor
Nowadays VLSI circuits have become much advanced by overcoming many challenges such as extra power
consumption, but circuit aging along with process variations are still challenging the advancements in power
efficient VLSI circuits. The aim of this dissertation is to propose the new adaptive technique to efficiently
compensate the fine grained variations by addressing the limitations in existing adaption approach. Adaptive
supply voltage (ASV) is proved to be one among the top most adaptation approaches in tuning of power
performance. Controlling power leakage is the main advantage in using ASV, while delivery overheads along
with voltage generation from conventional ASV systems make their application to mitigate fine-grained
variations demanding. The main aim of this dissertation is to present a dual level ASV system with band gap
reference Miniature programmable regulator (BGRMPR). Reference voltage independent of process and
temperature variations can be achieved because of using band gap reference voltage. Another advantage of
adapting this approach is because less power is consumed by system when compared to dual-level ASV system
with MPR.
Characteristics and Utilization Principle of Native Plants in HighwayIJERA Editor
Highway greening projects, in essence, is a kind of ecological restoration project. Plant as the prerequisite and
important material basis of ecological restoration, the choice and utilization of plant is the key to the success of
green. In the current green design, this part also has many problems. Therefore, this paper puts forward the
definition of native plants in ecological theory, and summarizes the characteristics and the use of different types of
plants.
Structural Vibration Control Using Solid Particle DamperIJERA Editor
In this paper the effectiveness of a solid particle damper to control structural vibration is experimentally
investigated. The vibration control performance and its influencing parameters are examined by a Multi Degree
of Freedom (MDOF) structure attached with a particle damper (PD) under horizontal excitation. In a particle
damping system damping is achieved using solid particles or granules and is a passive damping method. Here
the enclosure filled with particles is attached to the primary structure undergoing vibration. As the primary
structure vibrates, particles undergo inelastic collision within the enclosure resulting high amount of energy
dissipation. Based on the analytical study of undamped frame in ANSYS WORKBENCH, dimensions of the
frame were fixed and shake table study of a two storied steel frame with and without damper system are carried
out. Results shows that effectiveness of damping depends on various parameters like mass, particle size, shape
etc. The effectiveness is compared with a friction damper (FD) and is observed that PD is more efficient than
FD since 31.80% energy is dissipated more in PD compared to FD
A Combination of Wavelet Artificial Neural Networks Integrated with Bootstrap...IJERA Editor
In this paper, an iterative forecasting methodology for time series prediction that integrates wavelet de-noising
and decomposition with an Artificial Neural Network (ANN) and Bootstrap methods is put forward here.
Basically, a given time series to be forecasted is initially decomposed into trend and noise (wavelet) components
by using a wavelet de-noising algorithm. Both trend and noise components are then further decomposed by
means of a wavelet decomposition method producing orthonormal Wavelet Components (WCs) for each one.
Each WC is separately modelled through an ANN in order to provide both in-sample and out-of-sample
forecasts. At each time t, the respective forecasts of the WCs of the trend and noise components are simply
added to produce the in-sample and out-of-sample forecasts of the underlying time series. Finally, out-of-sample
predictive densities are empirically simulated by the Bootstrap sampler and the confidence intervals are then
yielded, considering some level of credibility. The proposed methodology, when applied to the well-known
Canadian lynx data that exhibit non-linearity and non-Gaussian properties, has outperformed other methods
traditionally used to forecast it.
Geo Environmental Investigation of Abuad Dumpsite, Southwestern NigeriaIJERA Editor
Geoenvironmental study of ABUAD female dumpsite was conducted to investigate the suitability of its location
and potential impact on groundwater in the environment. Profiling and Vertical electrical sounding methods
were employed using Dipole - Dipole and Schlumberger configuration respectively. Five points were sounded
and one profile was occupied. Three heterogeneous subsurface lithologic units were established namely; lateritic
topsoil, clayey-sand, and, fresh basement. The curve types are simple H and HA. The topsoil and clayey-sand
materials are characterized with relatively low resistivity values while the fresh basement materials are
characterized with high resistivity values. The average resistivity and thickness values for the topsoil are
280.0Ωm and.2.3m respectively. Clayey-sand was encountered in all the locations with average resistivity and
thickness values of 32.0Ωm and 7.3m respectively. Basement is relatively shallow in the study area, it was
encountered in all the locations with an average resistivity and depth values to the top of basement of 674Ωm,
and 9.6m respectively. Overburden materials are relatively thin within the area with an average resistivity and
thickness values of 156Ωm, and 9.6m respectively. The overburden materials constituting the aquiferous units
within the study area are porous, vulnerable, and good paths for leachate migration. The relatively low
resistivity values within the clayey-sand layers (14 - 61Ωm) are suggestive of leachate intrusion, while relatively
high resistivity values of the impervious basement are due to their crystalline nature. The proximity of the
dumpsite to both the cafeteria and residential halls is a cause for concern.
Collapse Behaviour and Energy Absorption of Aluminium Tubes Filled with Wood ...IJERA Editor
Experiments on filled and empty circular thin walled Aluminium AA6063 tubes with varying L/D ratios have
been performed to study load compression and energy absorbed for quasi static axial and oblique loading.
Dependence of deformation characteristics and energy absorption responses have been studied. Energy
absorption was measured from load-displacement graph obtained from UTM using MATLAB. Tubes were
clamped at the lower end and axial and oblique loads were applied by applying a force at upper end with
different angles to the centreline of column. Peak loads and absorbed energies have been compared for filled
and empty tubes for same L/D ratio. Experimental results are used to determine energy absorption capacity due
to plastic deformation of thin walled tube. The goal of the research was to study the interaction between the
forming and crash response of Al AA6063 in order to evaluate its potential for use in vehicle design for
crashworthiness.
A Mathematical Model to Solve Nonlinear Initial and Boundary Value Problems b...IJERA Editor
In this paper, a novel method called Laplace-differential transform method (LDTM) is used to obtain an
approximate analytical solution for strong nonlinear initial and boundary value problems associated in
engineering phenomena. It is determined that the method works very well for the wide range of parameters and
an excellent agreement is demonstrated and discussed between the approximate solution and the exact one in
three examples. The most significant features of this method are its capability of handling non-linear boundary
value problems.
Performance and evaluation of desiccant based air conditioning system.IJERA Editor
This Project work presents study and experimental analysis of Desiccant based air conditioning system.The main purpose of this project is to increase the efficency of air conditioning system.In the convenstional air conditioning system cooling coli has two load latent load and sensible load. Cooling has to cool the air and simultaneously to dehumidify it.It increases load on cooling coil and affects performance to the system. To increase the efficiency the air conditioning system desiccant materials are used at the inlet of the air conditioning test rig. Desiccant materials attract moisture based on differences in vapor pressure. Due to their enormous affinity to absorb water and considerable ability to hold water. Due to use of desiccant material load on the cooling coil reduces since moisture is absorbed by desiccant; cooling coil has to take only sensible load. Analysis is done using different desiccant materials and based on the observation, power consumption before and after desiccant is calculated. From this conclusion is made that desiccant material improves the efficiency of air conditioning test rig
Performance evaluation of an incorporation of a compact liquid desiccant syst...eSAT Journals
Abstract The primary goal of this paper is to suggest incorporation of a compact liquid desiccant system into an evaporative cooling-assisted 100% outdoor air system as an alternative proposal to the traditional vapor compression refrigeration system, especially with small loads, as well as to counteract the variation of climates. Current study presents an experimental analysis for building air conditioning system with using a LiCl aqueous solution as a liquid desiccant. Four air flow rate values are used for obtaining variable values of cooling capacity. Thermal and electrical COP is adopted to evaluate the system performance. The proposed system has the ability to improve indoor air quality, energy saving and environmental protection. Keywords: Air conditioning; Liquid desiccant; Evaporative cooling; 100% Outdoor air; Energy saving
In this communication, performance solar air
dehumidifier has been studied for Kota, Rajasthan.
The experimental set up was built in laboratory at
UCE RTU Kota. The parametric study has been
carried out in the year of 2014-15, in which
desiccant inlet temperature, air inlet temperature, air
flow rate, desiccant flow rate are studied. The
experimental results expressed in terms of graphical
method and found that by increasing regeneration
temperature of desiccant improves the moisture
absorption capacity of air, which decreases the
cooling load of air conditioner. This concept is
working on solar energy and it is fou
Thermodynamic Analysis of Cooling Tower with Air to Air Heat Exchanger for Re...IJMREMJournal
In this paper a thermodynamic analysis of cooling tower with air-to-air heat exchanger is presented. During
manual operation of conventional cooling tower, a good quantity of water is evaporated which requires equivalent
amount of makeup water for their condensers. So, in this regard, the thermodynamic model of a cooling with an
air to air heat exchanger is developed using engineering equation solver (EES) software and then simulated in
different climatic conditions of two major cities of Pakistan namely Karachi and Jamshoro through the period of
June & December 2017. The results show a significant variation in water vapor recovery with respect to
atmospheric conditions mainly humidity and ambient air temperature. Results reveal that the when a cooling
tower coupled with air to air heat exchanger maximum amount of water vapors are recovered at Karachi and
ranges up to 67% and 62% in Jamshoro during the month of December.
Thermodynamic Analysis of Cooling Tower with Air to Air Heat Exchanger for Re...IJMREMJournal
In this paper a thermodynamic analysis of cooling tower with air-to-air heat exchanger is presented. During manual operation of conventional cooling tower, a good quantity of water is evaporated which requires equivalent amount of makeup water for their condensers. So, in this regard, the thermodynamic model of a cooling with an air to air heat exchanger is developed using engineering equation solver (EES) software and then simulated in different climatic conditions of two major cities of Pakistan namely Karachi and Jamshoro through the period of June & December 2017. The results show a significant variation in water vapor recovery with respect to atmospheric conditions mainly humidity and ambient air temperature. Results reveal that the when a cooling tower coupled with air to air heat exchanger maximum amount of water vapors are recovered at Karachi and ranges up to 67% and 62% in Jamshoro during the month of December.
Operation of Solar and Waste-heat Powered Adsorption Desalinationiskandaruz
W.G. Chun1, K. Chen2, K. C. Ng3
1Department of Nuclear & Energy Engineering, Jeju National University, Jeju, Republic of Korea
2Department of Mechanical Engineering, University of Utah, Salt Lake City, Utah, USA
3Department of Mechanical & Production Engineering, National University of Singapore, Singapore
using different refrigerants as working fluid,the variation in the dimensional parameters of evaporator ,compressor,condenser and expansion device are shown.
Performance Enhancement of an Air Conditioner with Condensate Mist Cooled Con...IJMTST Journal
This paper presents a simple and efficient methodology to design a household (and can also be used for
commercial air conditioning purposes) air conditioner, predicts the performance of air conditioning unit and
how the thermal performance can be improved, when the water mist system is coupled with the air cooled
conditioner as a pre-cool for condenser inlet air to increase the cooling capacity, and decrease the compressor
power consumption. Inputs for formulation include inlet air DBT and humidity ratio, air velocity, water
temperature and flow rate, and geometrical properties of evaporative medium. Generally air conditioning
units are used for small and medium scale residential buildings and the large units are used for the
commercial purposes. Therefore, more energy efficiency and lower cost are needed along with reliable control
for the air conditioning units. The influence of condenser and evaporator inlet air temperatures on the cooling
capacity and power consumption has been investigated and presented. It has been found that due to the
coupling of water mist with air cooled condenser, the cooling capacity of the air-cooled,air conditioner can be
increased up to 17.5%, and the compressor power consumption can be reduced up to 15.5%. Thus, it is
concluded that the application of water mist condenser, inlet air pre-cooling could increase the COP by up to
37%, especially when the ambient relative humidity is low[10].
Air Cooled condensers were first introduced in US
power industry in early 1970’s, but only during last 10-15
years number of installations greatly increased largely due to
growing attention being paid to environmental safety. Also,
growing demand for water for both domestic and industrial
use has brought an increased interest in use of Air Cooled
condensers. This is a review paper which studies the
performance of Air-cooled condenser under various operating
conditions it is found that there is degradation in performance
of air cooled condenser under high ambient temperatures and
windy conditions. The heat rejection rate of ACC also depends
on surface condition of fins and thus its performance is
reduced due to external fouling of finned tubes due to weather
conditions and by internal fouling from condensate (Ammonia
corrosion). A Hybrid (dry/wet) dephlegmator achieves major
enhancement in performance when ambient temperatures are
high. Also shading of condensers is done for air-conditioning
units to mitigate the adverse effect of high ambient
temperatures due to solar radiation. Now a day’s wind walls
are used to reduce the effect of high wind velocity .second
option is to increase the fan speed Fin cleaning plays an
important role in heat rejection. External cleaning improves
air side heat transfer coefficient. In order to improve the
performance of an ACC Flat tubes inclined at some angle to
horizontal can also be used in place of conventional circular
horizontal tubes so that an improvement in heat transfer rate
occurs.
Air Cooler. Evaporative air cooler. Desert Cooler. Outdoor cooler. Industrial...Pramod Khedekar
We offer complete range of Air Cooler or Evaporative Air Coolers or Industrial Air Coolers or Commercial Air coolers or Desert cooler or outdoor coolers. We are Outdoor air coolers supplier in Dubai, Abu Dhabi, Sharjah, Oman, Doha & UAE.
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ISSN : 2248-9622,Vol. 5, Issue 6, ( Part -2) June 2015, pp.98-108
www.ijera.com 98|P a g e
Energy consumption in air-conditioning; Improvement and
Reduction
ENG/ Yacoub Yousef Ahmad Alotaibi
" Public Authourity For Applied Education & Training"
Abstract
Anew technique to reduce latent heat to improve energy consumption in air-conditioning is by using Desiccant .
The aim of dehumidification process is to remove the water vapor from the processed air to liquid desiccants.
Dehumidification is considered as a key feature of HVAC systems for thermal comfort. Chemical
dehumidification is remove the water vapour from the air by transferring it towards a desiccant material
(adsorption or absorption). Results illustrate that the application of liquid desiccant in air conditioning can
improve indoor air quality, reduce energy consumption and bring environmentally friendly products, also. Lewis
number increased rapidly with the increase of solution concentration Therefore liquid desiccant air conditioning
systems are drawing more and more attention in recent years.
Keywords: HVAC systems; Dehumidification; Chemical desiccants; desiccants
Introduction
Energy consumption due to conventional air-
conditioning is very high, especially in hot, humid
areas. The total air-conditioning cooling load can be
divided into sensible and latent parts.
Two types of space loads affect building humidity
and temperature:
Sensible load this is the addition of heat to the
building space and comes from a variety of sources
(e.g., sunlight, envelope, people, lights, and
equipment). Latent load this is the addition of
moisture to the building space and comes from
multiple sources (e.g., infiltration, mechanical
ventilation, and occupant activities).
Cooling loads can be reduced by reducing a
building‘s sensible cooling loads by improving the
envelope, integrating properly sized daylighting
systems, reducing unwanted solar heat gains,
reducing internal heat gains, and specifying cooling
equipment with high nominal efficiencies.
Shaded by trees play a major role in sequestering
CO2 and delay global warming also; improving air
quality by reducing smog.
An inverter can be used in an air conditioning
system to reduce energy consumption by controlling
the speed of the compressor motor to drive variable
refrigerant flow in an air conditioning system to
regulate the conditioned-space temperature.
Electrically driven vapor compression systems
typically dehumidify by first overcooling air below
the dew-point temperature and then reheating it to
an appropriate supply temperature, which requires
additional energy.
Another dehumidification strategy incorporates
solid desiccant rotors figure(1)[1] that remove water
from air more efficiently than vapor compression;
however, these systems are large and increase fan
energy consumption due to the increased airside
pressure drop of solid desiccant rotors.
RESEARCH ARTICLE OPEN ACCESS
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Fig (1) solid desiccant rotors
A third dehumidification strategy involves high-
flow liquid desiccant systems. These systems
require high-maintenance mist eliminators to protect
the air distribution system from corrosive desiccant
droplet carryover[2]. These are commonly used in
industrial applications but rarely in commercial
buildings because of the high maintenance cost.
Low-flow liquid desiccant air-conditioning
(LDAC)[3] technology
provides an alternative solution with several
potential advantages over previous dehumidification
systems as it:
• Eliminates the need for overcooling and reheating
associated with vapor compression systems.
• Avoids the increased fan energy associated with
solid desiccant systems.
• Allows for more efficient ways to remove the heat
of sorption than is possible in solid desiccant
systems and Reduces the amount of liquid desiccant
needed compared to high-flow LDAC systems.
• Is smaller and allows more flexible configurations
than solid desiccant systems.
• Reduces the desiccant droplet carryover problem,
thereby reducing maintenance requirements
compared to high-flow LDAC systems.
• Consumes less energy per unit of water removed
from the ventilation airstream compared to other
systems in low-sensible heat ratio (SHR) situations
where low interior humidity is required
• Can reduce peak electricity demand compared to
vapor compression systems if thermal energy
sources such as natural gas, solar thermal energy,
and waste heat are used for regenerating the
desiccant
• Can shift loads by using relatively inexpensive
desiccant storage to delay regeneration until times
when thermal energy is readily available and
cheaper
• Reduces other energy loads through integrated
design; for example:
- In grocery stores, lowering humidity levels with
LDAC can also reduce loads on: (1) refrigeration
system compressors; (2) defrost heaters; and (3)
anti-sweat heaters (ASHs) on display case doors
- In swimming pools, using the heat of absorption to
warm the pool water while using the pool water to
remove the heat of absorption.
1.1 LDAC Technology
Types of LDAC technology can be most easily
distinguished based on how sensible and latent loads
are removed from the product airstream (or supply
airstream) the two most common types of LDAC
systems:
High-flow LDAC:The liquid desiccant flow rate is
optimized to remove the sensible and latent energy
from the process air stream. The heat and mass
exchangers for this technology involve flowing two
fluids: desiccant and air.
Low-flow internally cooled LDAC:The liquid
desiccant flow rate is optimized to absorb moisture
out of the air, and a third stream (either liquid or
refrigerant) is used to remove the latent and sensible
energy. The heat and mass exchangers for this
technology flow three fluids: coolant, desiccant, and
air.
1.2 Chemical dehumidification
Desiccants are materials with a high affinity for
water vapour and may be solid or liquid. Adsorption
is when the physical or chemical nature of the
desiccant, generally solid, remains un-changed in
the dehumidification process; absorption conversely
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is when a change occurs, generally with liquid
substances [4,5]. A common adsorption solid is
silica gel, which behaves like a sponge. In fact, its
structure is extremely porous; its internal surface per
volume unit is immense, approximately 250m²/cm³.
Adsorption desiccants are typically chemical
compounds, such as synthetic polymers, silica gels,
titanium silicates, natural or synthetic zeolites,
activated aluminas,‗‗silica +‘‘, etc. [6,7–11].
Common absorbents are various solutions of water
and ethylene glycol, LiCl, LiBr,CaCl2.In the context
under examination regenerative systems are being
dealt with, that is those for which the mechanism of
moisture removal is continuous. Air to be treated
before supplying in indoor ambient is called
‗‗process air‘‘. Chemical dehumidification
[4,6,12,13] is based on the migration of water
vapour from process air towards the surface of the
desiccant due to the difference in partial vapour
pressure (the value of pv is greater in humid air). It
may be observed that the pressure gradient is
orientated in this direction because the desiccant is
dry and cool; should the material become warm and
moist the pressure gradient is inverted and water
vapour migrates from the desiccant to humid air.
The typical cycle of the desiccants made up by three
steps, Fig. (2).
(A–B) in A the desiccant is cold and dry; removing
water from the process air, the surface pvgrows
reaching the pv value of the surrounding air; the
equality is reached in B state: the migration of the
vapor stops.
(B–C) the desiccant is removed from the process air,
heated and exposed to a different air
flow(regeneration air, which is then discharged in
atmosphere) the gradient changes its direction and
the migration of the water vapour occurs from the
desiccant towards the air current. Instate C the
humidity content has the starting value (A), but the
pv is much greater because of the high temperature
reached by the material.
(C–A) the material is cooled until the starting
temperature. The values of humidity content andpv
are restored. The cycle can be repeated.
Liquid desiccant systems have also been suggested
as a way to shift latent loads to times when energy is
cheaper and/or renewable or waste energy is
abundant. Latent load shifting can be accomplished
with liquid desiccant, which is a relatively
inexpensive form of storage. Liquid desiccants can
also be used for removing biological and chemical
pollutants from process airstreams thereby
improving indoor air quality.
The desiccant can be used either in a stand-alone
system or coupled judiciously with a vapour
compression system to achieve high performance
over a wide range of operating conditions. LDAC
technology may provide additional energy savings
by allowing the main cooling system‘s evaporator
temperature to be set higher, which lowers the
cooling load and associated energy consumption. It
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should be possible to downsize the sensible cooling
system for new buildings and major HVAC retrofits.
As an example, reducing the indoor relative
humidity (RH) from 55% to 35% was shown in one
study to reduce the latent load and compressor
power demand of open vertical dairy cases by 74%
and 19.6%, respectively; the RH reduction also
reduced defrost duration by 40% (Faramarzi et al.
2000). Another benefit is that store managers may
be more willing to install refrigerated case doors
because product view will remain unobscured by
fog or frost. Case doors reduce the load on the food
refrigeration systems.
Fig.(3) shows three of the main components of the
LDAC system: the conditioner, the regenerator, both
are shown in the top portion of the fig. (3). And the
economizers shown in the bottom portion of the fig.
(3).
Figure 3 show a 3-D schematic diagram of low flow LDAC
1.3The system cools the air via the following
steps:
1. Hot-humid outdoor air (OA) (process air) enters
the conditioner and flows past the film of liquid
desiccant flowing down the flocked external
surfaces of each plate. The plates of the system are
configured as a water-cooled (internal to each plate)
parallel-plate heat exchanger.
2. The air is dried as water vapor from the air is
absorbed into the desiccant. The diluted desiccant is
then pumped to the regenerator. Now the dry air is
further cooled by a standard vapor-compression
evaporator coil or chilled water coil if needed and
then supplied to the space.
3. Scavenging air (usually OA) enters the
regenerator and contacts the diluted desiccant
flowing down the plates (much like the conditioner
working in reverse). The plates and the desiccant are
heated by hot fluid (water or glycol) flowing in the
plates to help the water desorb from the desiccant.
4. The scavenging air picks up the desorbed
moisture and is exhausted to ambient.
The thermal energy required for regeneration can be
provided by fossil fuel boilers; solar thermal
collectors; or heat recovered from reciprocating
engine generators, micro turbines, turbines, fuel
cells, or other processes with recoverable heat at
(150°–210°F)[14]. The desiccant used in LDAC
systems is most often lithium chloride (LiCl). In
some cases calcium chloride (CaCl
2
) is used because
it is significantly cheaper, which is especially
advantageous in applications where more than about
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(60) minutes of desiccant storage is needed;
however, CaCl
2
cannot dry air as deeply as LiCl.
1.4 Energy, cost breakdown, and comfort
benefits
• Heating, cooling, and fan energy savings: Heating
energy savings were negligible. Some small benefit
may be gained by adding complex control strategies,
which take advantage of the latent heat of
vaporization generated in the LDAC conditioner
during the heating season; however, this was not
modeled in this work and thus heating savings are
minimal. Cooling energy is reduced because the
need for overcooling with the vapor compression
system is eliminated by removing the latent load
from the ventilation air upstream of the cooling
coils. Fan energy savings are realized from fewer
cooling runtime hours.
• Lower average RH:Table(1)shows the annual
average RH in the zones treated by the LDAC for
the case with electric reheat coils. This example
shows that the RH levels are lower in the LDAC
models because the LDAC was controlled to
provide the driest air possible so that the
refrigeration system does not waste energy
dehumidifying the zone air. Although a control
strategy could be devised to maintain similar RH
levels for the two models, we elected to use realistic
and different control strategies for the baseline and
the LDAC. This resulted in conservative savings
estimates because the baseline systems were not
forced to produce the low humidity levels achieved
with the LDAC. Lower RH levels lead to better
product preservation by avoiding frost buildup on
frozen foods and moisture collection in packaged
baked good
wafra Kuwait city abdali
Baseline LDAC Baseline LDAC Baseline LDAC
60% 51% 58% 47% 62% 52%
Table 1
1.5 Effects of air humidity ratio on mass transfer coefficient and Lewis number
Liquid desiccant dehumidification is a nonlinear process because of two reasons: one is coupled heat and mass
transfer during the process and the other is that the important properties of the air and desiccant solution – hC,
hDare changing because of different parameters of inlet air and solution. Two sets of experiments were carried
out with different air humidity ratio, shown in Table (2).Fig. (4a) represents the effects of the air humidity ratio
on the mass transfer coefficient and Lewis number. The mass transfer coefficients are greatly dependent on the
air humidity ratio.
The mass transfer coefficients increased twice as faster as the increase of the humidity ratio from 7.3 to 10.97
g/kg at the air flow rate of 0.255 m3
/s. The Lewis numbers reduced rapidly from 10 to 4. Fig. 4b shows the
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effects of the higher humidity ratio on the mass transfer coefficients with the humidity ratio from 10 to 16 g/kg
and an air flow rate of 0.118 m3
/s. Whereas, the Lewis number was nearly constant and kept around (1.3). From
the results of Fig. (8), it is concluded that the mass transfer coefficients increase rapidly with the increase of the
air humidity ratio, but the Lewis number reduce at different rates.
1.6Effects of desiccant concentration on mass transfer coefficient and Lewis number
The experiment conditions were shown in Table (3). In this set of experiment, the thick solution with the
solution concentration Xs= 40.2% was confected by 30 kg LiCl dissolved into 44.6 kg pure water. The solution
absorbed the water from the air and became diluted, and the diluted solution was pumped into the dehumidifier
again till the solution concentration was less than 35%. Therefore, the solution with some different
concentrations could be tested
Fig. (5)presents the effects of the desiccant concentration on the mass transfer coefficient and Lewis number.
The figure indicates that the mass transfer coefficients increased obviously by increasing the mass concentration
of the solution. The mass transfer coefficient was about only 2g/(m2
s) at the solution concentration of 34.7%,
whereas the hD was about 21g/(m2
s) at the solution concentration of 40.2%, which was more than 10 times of
the former. This is just the reason of desiccant solution with high concentration yielding good dehumidification
performance. Also, the results showed the Lewis number increased rapidly with the increase of solution
concentration. When the concentration of desiccant solution was nearly 40%, the Lewis number was about 1.7.
The schematic diagram of the liquid desiccant dehumidification setup is shown in Fig. (6). It is made up of a
dehumidifier, a pump, a concentrated solution tank, a diluted solution tank, a Rota meter, etc. Two liquid
desiccant tanks(Tank 1 and Tank 2) are cylinders with the same dimensions,(70) cm in height and (55) cm in
diameter. Before experiments, valve (5, 6) used for drainage were close and liquid desiccant solution with the
weight concentration of about39% was confected by(59) kg of lithium chloride granular dissolved into 92 kg
pure water and poured into the Tank1. After closing the valve (1, 4) and opening the valve (2, 3)
dehumidification experiments started, and the liquid desiccant solution was transported from the Tank (1) to the
dehumidifier by the pump and collected in the Tank( 2). Until the Tank( 1) was emptied out, the desiccant
solution was pumped again via the dehumidifier from the (Tank 2 to the Tank 1) by opening the valve (1,4) and
closing the valve(2, 3) and so repeated. The inlet temperature of the solution entering into the dehumidifier was
controlled by the cooler and the electric heater which was controlled by a temperature controller. The flow rate
of the solution was adjusted by the valve (3or4). An environmental chamber was used for providing the air with
different temperature and humidity. The environmental chamber provided the measuring instruments for the
flow rate, dry-bulb temperature and wet-bulb temperature of the air, respectively. The dry-bulb and wet-bulb
temperature at outlet point were measured by(T4) and (Ts2). Temperatures of the desiccant solution at inlet point
and outlet point were measured by (T1) and (T2).
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Calculation
The latent ton-hours per scfm in a given hour are calculated as
follows:
We have chosen to define the ―space-neutral‖ conditions as 75°F (24°C), 50%RH (65 gr/lb[39 g/.45 kg])[3]
4.5 = lbs of air per hour per cfm.
7000 = grains of water vapor per lb.
1050 = heat of vaporization of water at standard temperature and pressure in Btu per lb.
12000 = represents the Btu‘s per hour of one ton of air conditioning capacity
The values for each of the 8760 hours of the year are calculated and summed to form the latent
(dehumidification) load portion of the index.
For desiccant wheels, Jurinak model[15] have been selected for the performance analysis as following
Where subscripts s and e means supply and exhaust, respectively, and( i, o) inlet and outlet respectively is
temperature in K and w humidity ratio in kg/kg. the desiccant wheel effectiveness mainly depend on the
material, wheel structure, and rotary wheel speed based on our finite difference analysis [16] of desiccant
wheels, at the optimum rotary speed, ɳғı is 0.30 and ɳғ2is 0.85 for 2.5 kg honeycomb desiccant wheel. Other
characteristics of the wheel are: duct wall thickness, 0.2 mm; duct geometry, sinusoidal; material, silica gel;
effective material fraction, 0.7; wheel length, 0.2m
heat and mass transfer coefficients hC, hDwere developed as following by regression method:
where Ua is the velocity of the air entering the packing, m/s. In the correlations the flow rate of the solution is
permitted to ignore considering that it is very little but enough to wet the packing.
If the process uses hot water or steam to achieve a latent coefficient of performance (COP) of 0.8– 0.94
depending on ultimate desiccant concentration. Latent COP is defined as:
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COP is maximized by maximizing the regeneration temperature and change in concentration while minimizing
the ultimate desiccant concentration. Including the COP of the water heater (about 0.82), a typical combined
latent COP is 0.82 × 0.85 = 0.7.
In summer the humidity ratio of outside air is normally higher than the indoor humidity ratio: therefor
dehumidify is a demand. For example, the indoor comfort conditions are Tdb = 25Cº and ϕ = 50%, (i.e. ωr =
10gv/kga) and the outdoor air design conditions are Tdb = 32Cº and ϕ= 55%, (i.e. ωo = 16.5gv/kga), the
humidity ratio of the supply air must be:
ωs<ωr =10 gv/kga<ωo =16.5 gv/kga
and the dehumidification system must be able to reduce the ω = 16.5gv/kga to ωs. In steady state, from the mass
balance for water, referred to a conditioned ambient with N occupants, it is obtained:
The humidity ratio of the airflow to be supplied must be equal to indoor airflow humidity ratio minus the ratio
between unitary mass flow rates (referred to each occupant) of water vapour and air. Referring to the case under
examination, and assuming the following values as indicative [17]:
mvu = 60g/h _ρa = 1.17kg/m³ Vau =10dm³/s it follows that:
ωs = 10gv/kga – 1.4gv/kga=8.6gv/kga → T dp;s = 11.8C°
So, the dehumidification capacity, in terms of humidity ratio variation, must beΔω = 16.5 – 8.6 = 7.9gv/kga
It can be noted that only the 18% (1.4/7.9) of Δω is due to the indoor load, while 82% is due to the outdoor air.
The dehumidification capacity (DC) usually expresses the water mass flow rate removed from the handled air
flow [18]. In steady state, from the water mass balance referred to the dehumidifier, one can obtain:
DC = ṁw = ṁaΔωDE = ρaᴠaΔωDE (10)
To express, as usual, DC in [kg/h] units, in Eq. (10) the following units are used: ρa [kg/m³], ᴠa[m³/h], ω
[kgv/kga]. It can be observed that the unitary capacity is equal to the humidity ratio variation:
Many building and furniture materials are known to be hygroscopic, thus the way in which air is supplied may
give rise to condensation and would growth. It would be advisable to mix treated air with ambient air in order to
increase temperature, thus preventing extremely cold air from coming into contact with surfaces, so avoiding
condensation.
conclusions
In operating conditions, hybrid systems based on chemical dehumidification permit to control separately both
temperature and humidity (the DW is connected to a humidity sensor, the CC to a temperature sensor). On the
contrary, in traditional cooling systems only temperature is generally directly controlled (DBTCS), while
humidity can vary.
Systems based on chemical dehumidification allow to reduce humidity even when required dew point
temperature is very low, so allowing an easier balance of high latent loads. On the contrary, conventional
systems can dehumidify air stream generally only for required dew point temperatures higher than 4Cº.
The technology based on chemical dehumidification, reducing electric power and energy requirements and the
CFC and HCFC refrigerant fluids use, is characterized by a low environmental impact. Desiccant technology is
a promising alternative for dehumidification.
Temperature and humidity of outdoor air have great effect on energy consumption and on COP. The energy
consumption increase with the rising of the temperature and humidity of the outdoor air and COP decrease,
also; more ventilation air flow rate, more energy consumption and lower COP.
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Acronyms and Abbreviations
AHU air handling unit
ASH anti-sweat heater
ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers
CaCl
2
calcium chloride
CC cooling coil
cfm cubic feet per minute
CHP combined heat and power
COP coefficient of performance
DB dry bulb temperature
DBTCS control system based on dry bulb temperature
DC Dehumidification capacity
DP dew point temperature
DW DW desiccant wheel
DX direct expansion
hc heat transfer coefficient (W/(m2 _C))
hD mass transfer coefficient based on air humidity
hp horsepower
HR humidity ratio
HVAC heating, ventilation, and air conditioning
LDAC liquid desiccant air-conditioning
Le Lewis number, dimensionless
LHR latent heat ratio
LiBr lithium bromide
LiCl lithium chloride
MCBD mean coincident dry bulb temperature
MRC moisture removal capacity
NREL National Renewable Energy Laboratory
OA outdoor air
RH relative humidity
RSHI regeneration specific heat input
SCFM Standard cubic feet per minute
SHR sensible heat ratio
TMY3 Typical Meteorological Year 3
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