This document outlines the design of a heat exchanger system for a fireplace. The objective is to recover heat from the fireplace that would otherwise be lost up the chimney. The design involves running copper pipes around the back of the fireplace through which water will circulate. Calculations are shown to determine the heat transfer and optimize the design to heat the water to 180°F. The total cost of materials is estimated to be $3,400, and the system is expected to last 50 years if installed properly.
In this work a sample problem for shell and tube heat exchanger is analytically solved to size the heat exchanger and thereafter perform cfd validation study .
This presentation contains an overview of tracking plant performance, with its application in two case studies, including gas compression train monitoring (Aspen) and production facility surveillance system (HYSYS).
In this work a sample problem for shell and tube heat exchanger is analytically solved to size the heat exchanger and thereafter perform cfd validation study .
This presentation contains an overview of tracking plant performance, with its application in two case studies, including gas compression train monitoring (Aspen) and production facility surveillance system (HYSYS).
Definition and Requirements
Types of Heat Exchangers
The Overall Heat Transfer Coefficient
The Convection Heat Transfer Coefficients—Forced Convection
Heat Exchanger Analysis
Heat Exchanger Design and Performance Analysis
A heat pipe is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between two solid interfaces.
The COP of the refrigeration increasing the performance and to get high efficiency of the refrigeration system. By using nano coating over the evaporator of the refrigeration component the objective can be achieved. The improper heat dissipation occurred in the heat exchanger components causes effect in performance. The vapour compression refrigeration system consuming the high power. Though the energy taken for the refrigeration process has increased and leads to more power consumption. In order to increase the performance, Nano coating Copper Oxide has been applied over the evaporator. By applying the Nano coating Copper Oxide over the evaporator the COP increased. In result the energy required for the refrigeration process and global warming problems has been reduced. By addition of nanoparticles to the refrigeration results in improvements in the COP of the refrigeration, thereby improving the performance of the refrigeration system. In this experiment the effect of using CuO-R134a in the vapour compression system expected COP will be increased by 5% with nano coating.
ME 438 is a course taught by Dr. Bilal Siddiqui at DHA Suffa University. This set of lectures deals with review of vector calculus, fluid mechanics, circulation, source/sink method, introduction to computational aerodynamics with source panel method and calculation of lift.
Questions and answers on turbines used in Power Plants. The discussion is definitely going to reduce your doubts and give you all answers on your questions. This is part 1 and the series will be continued till your doubts are cleared. you can mail me the questions and i will try to give you all answers as early as possible.
This presentation is a brief descriptive procedure of simulating in aspen flare system analyser (otherwise called as flarenet). It gives a step by step instructions to develop a flare network scheme in the simulator
Understand the physical mechanism of convection and its classification.
Visualize the development of velocity and thermal boundary layers during flow over surfaces.
Gain a working knowledge of the dimensionless Reynolds, Prandtl, and Nusselt numbers.
Distinguish between laminar and turbulent flows, and gain an understanding of the mechanisms of momentum and heat transfer in turbulent flow.
Derive the differential equations that govern convection on the basis of mass, momentum, and energy balances, and solve these equations for some simple cases such as laminar flow over a flat plate.
Non dimensionalize the convection equations and obtain the functional forms of friction and heat transfer coefficients.
Use analogies between momentum and heat transfer, and determine heat transfer coefficient from knowledge of friction coefficient.
Definition and Requirements
Types of Heat Exchangers
The Overall Heat Transfer Coefficient
The Convection Heat Transfer Coefficients—Forced Convection
Heat Exchanger Analysis
Heat Exchanger Design and Performance Analysis
A heat pipe is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between two solid interfaces.
The COP of the refrigeration increasing the performance and to get high efficiency of the refrigeration system. By using nano coating over the evaporator of the refrigeration component the objective can be achieved. The improper heat dissipation occurred in the heat exchanger components causes effect in performance. The vapour compression refrigeration system consuming the high power. Though the energy taken for the refrigeration process has increased and leads to more power consumption. In order to increase the performance, Nano coating Copper Oxide has been applied over the evaporator. By applying the Nano coating Copper Oxide over the evaporator the COP increased. In result the energy required for the refrigeration process and global warming problems has been reduced. By addition of nanoparticles to the refrigeration results in improvements in the COP of the refrigeration, thereby improving the performance of the refrigeration system. In this experiment the effect of using CuO-R134a in the vapour compression system expected COP will be increased by 5% with nano coating.
ME 438 is a course taught by Dr. Bilal Siddiqui at DHA Suffa University. This set of lectures deals with review of vector calculus, fluid mechanics, circulation, source/sink method, introduction to computational aerodynamics with source panel method and calculation of lift.
Questions and answers on turbines used in Power Plants. The discussion is definitely going to reduce your doubts and give you all answers on your questions. This is part 1 and the series will be continued till your doubts are cleared. you can mail me the questions and i will try to give you all answers as early as possible.
This presentation is a brief descriptive procedure of simulating in aspen flare system analyser (otherwise called as flarenet). It gives a step by step instructions to develop a flare network scheme in the simulator
Understand the physical mechanism of convection and its classification.
Visualize the development of velocity and thermal boundary layers during flow over surfaces.
Gain a working knowledge of the dimensionless Reynolds, Prandtl, and Nusselt numbers.
Distinguish between laminar and turbulent flows, and gain an understanding of the mechanisms of momentum and heat transfer in turbulent flow.
Derive the differential equations that govern convection on the basis of mass, momentum, and energy balances, and solve these equations for some simple cases such as laminar flow over a flat plate.
Non dimensionalize the convection equations and obtain the functional forms of friction and heat transfer coefficients.
Use analogies between momentum and heat transfer, and determine heat transfer coefficient from knowledge of friction coefficient.
Heat exchangers are used widely in industrial application such as chemical,
food processing, power production, refrigeration and air-conditioning
industries. Helical coiled heat exchangers are used in order to obtain a large
heat transfer per unit volume and to enhance the heat transfer rate on the inside
surface. In the present study, CFD simulations are carried out for a counter
flow tube in tube helical heat exchanger where hot water flows through the
inner tube and cold water flows through the outer tube. From the simulation
results heat transfer coefficient, pressure drop and nusselt number are
calculated. The heat transfer characteristics of the same are compared with that
of a counter flow tube in tube straight tube heat exchanger of same length
under same temperature and flow conditions. CFD simulation results showed
that the helical tube in tube heat exchanger is more effective than the straight
tube in tube heat exchanger.
Numerical Simulation of a Tube in Tube Helical Coiled Heat Exchanger using CFDCarnegie Mellon University
Heat exchangers are used widely in industrial application such as chemical,
food processing, power production, refrigeration and air-conditioning
industries. Helical coiled heat exchangers are used in order to obtain a large
heat transfer per unit volume and to enhance the heat transfer rate on the inside
surface. In the present study, CFD simulations are carried out for a counter
flow tube in tube helical heat exchanger where hot water flows through the
inner tube and cold water flows through the outer tube. From the simulation
results heat transfer coefficient, pressure drop and nusselt number are
calculated. The heat transfer characteristics of the same are compared with that
of a counter flow tube in tube straight tube heat exchanger of same length
under same temperature and flow conditions. CFD simulation results showed
that the helical tube in tube heat exchanger is more effective than the straight
tube in tube heat exchanger.
The objective of this experiment is to calculate the rate of the heat transfer log mean temperature difference, and the overall heat transfer coefficient in case of Counter flow
Numerical Analysis of Heat Transfer Enhancement in Pipe-inPipe Helical Coiled...iosrjce
These paper focuses on the effect of the inside tubes at constant value of mass flow rate and variation
of annulus mass flow rate on effect of Dean Number and overall heat transfer coefficient with constant wall
temperature, CFD analysis of a helically coiled heat exchanger. Also deals with the effect of Dean Number with
respect to Reynolds Number and Nusselt Number and Overall Heat Transfer coefficient on change of coil
configuration of helically coiled tube. The particular difference in this study in comparison with the other
similar studies was the boundary conditions for the helical coils. The results indicate that with the decrease the
inner coil diameter, the overall heat transfer coefficient is increased
Aim:
To determine the heat loss in a double pipe heat exchanger counter-current flow
experiment.
Theory:
A double-pipe heat transfer exchanger consists of one or more pipes placed
concentrically inside another pipe of a larger diameter with appropriate fittings to direct
the flow from one section to the next. One fluid flows through the inner pipe (tube side)
in this experiment (hot water), and the other flows through the annular space (annulus)
(cold water).
The double-pipe heat exchanger is one of the basic kinds of exchangers with a very
flexible configuration. There are two types of counterflow or parallel flow for this type
that are the basis of design and calculation for determining pipe size, length, and
number of bends.
Double pipe heat exchanger counter current: heat is exchanged between two flowing
fluids at a different temperature that flows counter current in the heat exchanger double
pipe.
The efficiency is greater in counter-current than in parallel flow because the two fluids
(water) flow separately in counter-current flow when the high different temperatures
meet heat exchange rapidly due to the difference of temperatures, the hot water
becomes warm then cold as heat exchanges, and the cold water becomes warm the heat
exchange occurs till it reaches steady state. As it is explained in Figure 1.
Heat loss can be found by the equation below:
Q=ΔH=mCpΔT
Where: Q=ΔH is the amount of heat transferred to or from the system (J).
m: mass of the system (Kg)
Cp: constant pressure specific heat capacity of the system (J/g°C)
ΔT: difference in temperature of the system °C.
Experiment: Double pipe heat exchanger
4
Figure 1: concurrent and countercurrent respectively.
Procedure:
Double pipe heat exchanger: as shown in the figure-2:
1. Power switch: No.1
2. Temperature scale to select a temperature to heat the water in the tank [No.2] in
the figure.
3. Water tank a heating coil is used to heat the water [no.3].
4. Power pump to set a flow rate, the water is pumped through the double pipe heat
exchanger. [No.4]
5. A flow rate measurement is found in no.5
6. [No.6-7-8-9-10] The temperature measurements measure temperature
throughout the process.
7. Then the temperature and flow rate are collected in the temperature screen.
Experiment: Double pipe heat exchanger
5
Figure 2: double pipe heat exchanger.
Experiment: Double pipe heat exchanger
6
observation:
1. Turn on the device with the power switch.
2. The flow rate is set as 157 ml/s.
3. Heat water up to [40-50 Celsius] in this experiment: [44.4 Celsius] by the
heating coil in the water tank, set the desired temperature by the temperature
scale in the water tank.
4. Then water is pumped to the pipes by the power pump.
5. Adjust the valves so that the hot water and cold water flow countercurrent.
6. The hot water flows in the inner pipe in the double pipe through the pipe from
the pump to the heat exchanger
7. the cold water flows in the outer pipe counter current from the tank to the pipes
the valv
Submission for General Electric's FirstBuild and MakerBot's IceBox Challenge that tasked users to create a 3D-printable design that would benefit day-to-day refrigerator use.
3. 2
Objective and Introduction:
Our objective was to design a system for fireplace heat recovery. In most wood-burning
fireplaces, much of the heat that is not directly blown into the room ends up being lost through
the chimney and to the outside. Because the heat convected from a fire is dependent only in
the direction it is felt, we felt that the most valuable way to recover heat was to place water
pipes around the back of the fireplace. The introduction of a new temperature sink has no
effect on the heat that convects into the interior of the home, so we found this concept to be a
minimalistic design change to the standard fireplace structure.
In our research, we have found that most wood-burning fireplaces can reach steady
temperatures of 1100o
F to 1500o
F. By running pipes through the system, we effectively create
a heat exchanger system that can take advantage of the large amounts of heat energy that is
normally lost. By utilizing thermally conductive pipes that can withstand such high
temperatures, we can heat the flowing water to nearly a boil, lightening the load on the
residential boiler.
Heat exchangers are systems that have two fluids flowing adjacent to each other at
different temperatures. Because of the Zeroth Law of Thermodynamics, the fluid of higher
temperature will convect its heat across the heat transfer surface area to the fluid of lower
temperature. This process will continuously occur until the system reaches a temperature
equilibrium for both fluids, but the flowing nature of the fluids allow the system to exchange
heat indefinitely.
Design Criteria and Assumptions:
Our assignment consisted of designing a heat recovery system for a fireplace. Due to
the excessive heat energy that is wasted during the process, we approached the task by
designing a heat exchanger that would attempt to recover the lost energy and use it to assist a
residence’s boiler system. By having a secondary water-heating system available, it is possible
to lighten the load on the boiler and save on energy costs.
In the proposal of our design, many assumptions had to be made in order to allow our
experience with thermodynamics and fluid dynamics to properly apply to the system. For
example, our water-flow input was assumed to be turbulent and fully developed right from the
start. For the Extended Bernoulli’s Equation to apply, we assumed our pipe system to be
perfectly sealed, allowing a steady, incompressible, flow of water to be analyzed with continuity
analyses.
Had we not made these assumptions, we would not have the tools necessary to perform
the accurate calculations on such a complex system.
4. 3
Design Procedure:
We started the design by analyzing the two fluids of the heat exchanger: the fire-heated
air surrounding the pump-controlled water. In order to acquire an overall analysis of the
system, it was necessary to find the Overall Heat Transfer Coefficient.
(Eq. 1)
To find the convection coefficient of the water being heated, we utilize the velocity of
the water and its fluid properties to find the Reynolds Number. The temperature at which the
fluid properties are found is the Bulk Fluid Temperature (Table A-9E).
(Eq. 2 & 3)
With the dimensionless Reynolds Number, we can find the Nusselt Number.
(Eq. 4)
Because the Nusselt number is the ratio of conductive to convective heat transfer, we can
utilize it to calculate the Convective Heat Transfer Coefficient of the internal water flow.
(Eq. 5)
The process to find the convection coefficient of the heated air is actually different. This
is due to the fact that the air around the fire was assumed to be ambient, so we modeled that
fluid to be under free or natural convection. The major differences in analysis are the
utilization of the Film Temperature and the addition of the Coefficient of Volume Expansion.
(Eq. 6 & 7)
These new variables are used to find the Rayleigh Number, which is necessary to find the
Nusselt Number for natural convection systems.
( )
{
( ) ⁄
[ ( )
⁄
]
⁄
} (Eq. 8 & 9)
5. 4
The equation to find the Free Convection Heat Transfer Coefficient is then the same as that for a
forced convection system.
(Eq. 10)
With these individual convection heat transfer coefficients, the Overall Heat Transfer
Coefficient of the entire system can then be represented.
(Eq. 11)
Using this coefficient, we can use the heat exchanger equations to fully analyze the system.
( )
(Eq. 12 & 13)
The pressure analysis of the system was performed using the Extended Bernoulli’s
Equation.
∑ (Eq. 14)
However, the two points of our analysis occurs before and after the pipes split and reattach, so
there is no need to include change in height. Also, because the diameter of pipe at both
analysis points are the same, there is no change in fluid velocity as well. This allows our
equation to be simplified to the following:
∑ (Eq. 15)
in this equation refers to the output pressure of the pump we have selected. The pressure
of a pump is determined using the horsepower and volume flow rate with the relations:
( )( )
(Eq. 16)
(Eq. 17)
The added terms shown on the Extended Bernoulli’s Equation refer to the frictional losses and
the minor losses, respectively. These terms contribute to pressure drop in the system caused
by fluid friction against the sides of the pipe and the dynamics of fluids flowing through joints
and manifolds.
6. 5
Design Phase
Figure 1: Fireplace Heat Exchanger Piping system with Pump
After extensive research, the material chosen for the pipe was copper. In addition to its
low cost and high thermal conductivity, it was a standard component in many heating systems.
This was a safe material choice because wood fires burn at 1100o
F to 1500o
F [1]
, but the
melting point of copper is upwards of 1900o
F [2]
. Because our elbow joints and manifolds
would consist of welded connections, their ability to withstand temperature usage could last
indefinitely. However, during our calculations, we assumed that fouling would not occur.
Realistically, corrosion may become an issue in this system, as it does in all piping systems. We
chose a standard inner diameter pipe size of 2.465 inches [3]
, making it easily accessible if
components ever needed to be replaced.
The single pipe travels through a manifold that divides the flow of water into 7
individual pipes of equivalent area. This is done to decrease the speed of the flow and increase
surface area exposure to the fire, thus allowing more heat absorption as the water passes.
After passing along the walls of the fireplace, the pipes reemerge from the “heat exchanger”
and enter a second manifold that rejoins the flow of all 7 pipes. We decided this to be the best
course of action in order to simplify our fluid analysis as well as reduce the heat loss of the
water to the surroundings. As previously stated, the pipes are all welded to each other rather
7. 6
than connected via gasket threaded to ensure temperature resistance and stave off water
leakages.
According to the New York City Plumbing Code, the maximum water pressure within a
building is 85 pounds per square inch. When exceeded, a water-pressure reducer must be
installed. Given this information, we found it acceptable to use a 2-horsepower pump that
would supply a pressure of 38.56 pounds per square inch.
Results & Discussion:
In order to perform a proper analysis on the system to calculate all the relevant
information, assumptions were made in regards to the simplicity of the system. It was
presumed that the water flow was fully developed and turbulent and moving through a
smooth, corrosion-free pipe. In order to use Bernoulli’s equation, it was required to accept that
the fluid flow was steady and incompressible as well.
The air outside of the pipes is assumed to be subject to no external forces, so the
buoyancy of hot air is assumed to be the only motion taking place. This allowed us to model
the “shell-side” fluid in this “heat exchanger” as a free or natural convection system.
The initial condition of the pipe fluid was assumed to be 60o
F water flowing at 0.6 ft/s.
In order for the water to leave the system at the desired 180o
F, heat energy from the cross-
flow air must transfer to the water. The ambient heated air adjacent to the pipes was assumed
to be 200o
F, and after calculations, the outlet temperature of the air was found to be 148o
F.
This was done by finding the convection heat transfer coefficients for both fluids (hH20 = 194.5
BTU/h·ft2
·R and hair = 0.99 BTU/h·ft2
·R) and determining the heat transfer surface area to be the
surface area of the exposed piping (AS = 4.1667 ft2
). The total heat transfer rate of the system
( ) was found to be 146.25 BTU/s.
With the system being powered by a 2-horsepower pump, it was determined that the
volume flow rate through the 0.205-inch diameter pipe was 88.9 gallons per minute; it followed
that the pressure offered by this pump was measured to be 38.56 pounds per square inch. The
utilization of the extended Bernoulli’s equation allowed us to calculate a total pressure drop
from the beginning to end of the heat exchanger was only 3.15 pounds per square inch.
8. 7
Cost Analysis:
As with all upgrades and installations, it must be determined whether or not it is
financially feasible to make such renovations. Assuming that the fireplace infrastructure is
already in place, the additional costs involved consist of the piping system, the pump itself, and
labor.
Using Plumbing Supply as reference [5]
, the cost of Type “L” Rigid Copper Pipe with a
diameter of 2.5 inches is approximately $35.00 per linear foot. The pipe cost, excluding the
manifold, would amount to $2065.00 for 59 linear feet and $928.48 for 28x 90o
elbows.
According to Water Pumps Direct [6]
, a 2-horsepower pump rated for 89 gallons per minute
would cost $400.
Thus, the total cost of the pump and copper piping, excluding the custom manifolds and
the copper piping required to reconnect the system back to the main plumbing infrastructure,
would come out to $3400.00 before labor.
Conclusion & Recommendation:
Our design uses a heat exchanger to capture some of the lost heat given off by the fire.
The water in the pipes is heated with this lost energy, which can then be fed directly into the
boiler, essentially lessening the load on the water heating system. This can directly lead to
reduced energy costs and a more environmentally friendly system. Though we may not
recommend going out of your way to perform such an installation, if the renovation of a
fireplace was already intended, this could be a fiscally responsible move. If installed properly
this system should last at least 50 years under normal operating conditions [7]
.
9. 8
Appendix
Detailed derivations and calculations regarding the Shell Fluid (Heated Air)
Detailed derivations and calculations regarding the Tube Fluid (Water)
Detailed derivations and calculations regarding the Heat Exchanger as a whole
Detailed derivations and calculations regarding the Fluid Pressure of the system
1. http://homeguides.sfgate.com/temperatures-woodburning-stove-48039.html
2. http://www.engineeringtoolbox.com/melting-temperature-metals-d_860.html
3. http://www.petersenproducts.com/Specifications/Pipe_Copper.aspx
4. http://www.nyc.gov/html/dob/downloads/pdf/plumbing_code.pdf
5. http://www.plumbingsupply.com/copperpipe.html
6. http://www.waterpumpsdirect.com/pumps/2-hp-sprinkler-pumps.html
7. http://colerepair.com/Copper%20Water%20Pipe.html