30120140504016

228 views

Published on

Published in: Technology, Business
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
228
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
2
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

30120140504016

  1. 1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME 123 EXPERIMENTAL AND NUMERICAL INVESTIGATION OF AIRFLOW AND TEMPERATURE DISTRIBUTION IN A PROTOTYPE COLD STORAGE Qasim S. Mahdi, Husam Mahdi Hadi* Department of Mechanical Engineering, College of Engineering, Al-Mustansiriyah University ABSTRACT Airflow and temperature distribution inside a cold store are investigated using experimental and computational fluid dynamic using CFX 14.5. In the present work a prototype cold storage for meat has been designed. Temperature distributions were determined for different storage temperature, -2°C, -10°C, -20°C and -21°C, inside empty cold store experimentally. The Air temperature distribution also been determined for storage temperatures -20°C and -21°C inside loaded cold storage with 10.8kg. The Mean air velocity distribution also been measured for empty cold store, by using a hot wire anemometer. Navier-Stokes equations, and the turbulence is taken into account using a standard εκ− model, incompressible, symmetric cold store used to analysis the loaded and empty cold storage and the meat are presented as a solid domain with variable thermophysical properties as a function of temperature. Air flow distribution results in the three levels (bottom, medium and top) for empty cold store with relative error between experimentally and numerically equal to 20%. The relative error between the experimental and numerical for temperature distributions inside empty cold storage equal to 13%. Correlations have been developed for modeling the evaporator unit in numerical simulation, where the total error between the experimental results and the correlation that used in numerical is 8.8%. Keywords: Cold Store; Air Distribution; Temperature Distribution; CFX; Correlations for Modeling the Evaporator Unit. INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME: www.iaeme.com/ijmet.asp Journal Impact Factor (2014): 7.5377 (Calculated by GISI) www.jifactor.com IJMET © I A E M E
  2. 2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME 124 NOMENCLATURE UnitDescriptionSymbol Constant Coefficient in k- ε Model µC,C,C 21 MHydraulic diameterDh W/m.KThermal conductivityK N/m2 PressureP N/m2 Modified pressure'p STimeT (m/s)Velocity vectorU m/sVelocity Components in X,Y & Z Directions u,v,w Greek symbols m2 /sThermal Diffusivityα mDistance Between Scalar Quantities kji Z,Y,X ∆∆∆ (m2 /s3 )turbulence energy dissipation ε Turbulent intensityI (m2 /s2 )Turbulence kinetic energyκ (kg/m.s)Second viscosityλ N.s/m2 Dynamic Viscosityµ (kg/m.s)Effective viscosityeffµ (kg/m.s)Turbulent viscosityTµ kg/m3 Densityρ Empirical Constant ε σ κ σ , Dissipation functionΦ 1. INTRODUCTION Frozen storage requires freezing of the product and storage at the temperaturerange between - 12º C and -23º C. Different factors govern the ultimate quality and storage life of any frozen product, such as: (i) the nature and composition of the product to be frozen. (ii) The careful use in selecting, handling and preparing the product for freezing. (iii) The freezing method. (iv) The storage
  3. 3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME 125 conditions [1]. Therefore, the main aim in designing a storage system is to ensure a uniform targeted temperature and humidity in the bulk of storage product. The temperature distributions inside the cold store depend on the air flow distribution, where theydependon the product, the cooling medium, the geometry and characteristic of the cooling room. They are several studies on the experimental and numerical investigation of air flow, temperature such as: M.L. Hoang et al. [2] investigated theairflow inside a cold store using CFX package. The airflow model is based on the steady state incompressible, Reynolds-averaged Navier-Stokes equations.The standard as well as the Renormalization Group (RNG) version of the k- Ɛ model is investigated. Also, the finite volume method of discretization is used.Validation was performed by comparisons of numerical and experimental data on vertical profiles of air velocity magnitudes. The accuracy was 26% for the standard k–Ɛ model and 28.5% for the RNG. A transient three-dimensional CFD model was developed by H.B. Nahor et al. [3] to calculate the velocity, temperature and moisture distribution in an existing empty and loaded cool store. An average accuracy of 22% on the velocity magnitudes inside the empty cold store was achieved and the predicted temperature distribution found more uniform than the predicted results. In the loaded cold store, an average accuracy of 20% on the velocity magnitudes was observed. Serap Akdemir and Selcuk Arin[4] studied the spatial distribution of the ambient temperature, relative humidity and air velocity in cold store. Their results are achieved at ceiling, medium and floor level in the cold store and for different storage temperatures (0 ºC, 1 ºC, 2 ºC and 3 ºC). Mapping software was presented to show the variability. Also, they indicated that the spatial distribution of the temperature and the relative humidity was not uniform in the cold store. Bjorn Margeirsson and Sigurjon Arason [5] investigated the temperature monitoring in both cold stores and containers which are used for storage and transportation of frozen fish products. Numerical modeling of airflow and temperature distribution in one of the cold store was performed using the CFD code Fluent for both steady and unsteady.Seyed Majid Sajadiye et al. [6] used a multi-scale three-dimensional CFDcode fluent model, which predicts the airflow, heat and mass transfer in a typical full loaded cool storage. The model was validated against experiments by means of velocity, product temperature, and product weight loss measurements in cool storage. The errors of about 23.2% and 9.1% were achieved for velocity magnitude prediction in the cool storage and the product weight loss after 54 days of cooling in the loaded cool storage, respectively. 2. MODELING 2.1. Physical model The dimensions of the simulated cold store are100cm × 100cm × 100cm and the air cooling fan dimensionsare74.5 cm × 40 cm × 14.3 cm. The door of the cold store located at the middle of the front wall with dimensions, 57cm width, 67cm height and 5cm thickness. The structure of the cold store is made from polyurethane insulation layer, 10 cm thickness, and the dimensions of the cold store from inside are 80 cm × 80 cm × 80 cm. 2.2. Mathematical model To simplify the model, a number of assumptions were made: Transient condition as analysis type, total time (1800 second) and times steps (10 second) for empty cold store and steady state with 370 iterations for loading cold store; Negligible the natural convection; No heat flow through the door and walls; The Boussinesq model was not adopted; Three dimensional, Incompressible flow; The radiation between the side walls is ignored; Turbulence medium intensity equal (5%) and The air flow is assumed as steady turbulent state.
  4. 4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME 126 According to the above assumption, the following equations for air inside cold store are given [7,8]: ( ) )9(3.1;0.1;92.1 2 ;44.1 1 ;09.0 )8( 3.0 2/3 ,2)( 2 3 )7( 2 21 )( )6()( )5( 2 )4(2)( 2)( 2)(2)(2)(2)(2)(2 )3()()()( )( )2(2 ' )1(0 ===== × =×= −           ∂ ∂ + ∂ ∂ ∂ ∂ =         ∂ ∂ ∂ ∂ − ∂ ∂ + ∂ ∂ −           ∂ ∂ + ∂ ∂ ∂ ∂ =         ∂ ∂ ∂ ∂ − ∂ ∂ + ∂ ∂ = +               ∂ ∂ + ∂ ∂ + ∂ ∂ + ∂ ∂ + ∂ ∂ + ∂ ∂ +      ∂ ∂ + ∂ ∂ + ∂ ∂ =Φ Φ++−=+ ∂ ∂ ∇+ ∂ ∂ −= ∂ ∂ +      ∂ ∂ =      ∂ ∂ + ∂ ∂ + ∂ ∂ + ∂ ∂ ε σ κ σ µµµ ε ρ κ ε µκ ε µ ε ε σ µ ερ ρε ρεµ κ κ σ µ κρ ρκ ε κ ρ µ µ νλµ ννρν ρ µρ ρ ρ CCC h D k IUk C i x j U j x i U j x i U C j x T j xj U j xt i x j U j x i U j x i U T j x T j xj U j xt C T Udi y w z v x w z u x v y u z w y v x u stateof Equations gradTkdiUdipTUdi t T Energy U ieffx i p U jU i x jt U i z w y v x u t Continuity 2.3. Initial Boundary Condition The initialization of the model is important for convergence. If the initial conditions are poor, then it takes longer to converge or it may even result in divergence. In the present work the initial conditions are: 1- The Cartesian velocity components (U=0, V=0 and W=0) all in m/s. 2- Relative pressure (0) Pa. 3- All variable are initiated for different temperature dependent on the initial experimental temperature for each case as follows: a- The initial temperature inside the empty cold store is 30º C. b- The initial temperature inside the loaded cold store is 32º C and 35ºC for six meats distributed in three levels. 2.4. Boundary conditions The air velocity and temperature inlet boundary condition a, which are suggested 3.2m/s and ( evaporatorfromOutletT ) respectively for empty cold store, and 3.2m/s and -21º C for loaded cold store, are used in the present work. Where the velocity and temperature open boundary condition are determined experimentally. These include velocity type Cartesian with insert automatic, with value (U=0 m/s, V=0 m/s and W=1.78 m/s), the opening temperature ( evaporatortoInletT ) for empty cold store
  5. 5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME 127 and the opening temperature -21º C for loaded cold store. Also, the other side inside the cold store, which is symmetry in a boundary condition, is considered the other half of evaporator fan and trays. All empirical equations are obtained using the multi-regression analysis technique and then submitted as an expression in CFX, which depends mainly upon the experimental measurements, from the inlet and outlet temperature of the evaporator. The empirical formulae of the outlet and inlet temperature from evaporator as a function of time t are respectively: sec]/[]sec/[6612763.0 sec]/[002296065.09077291.0][18583.27 ]sec/[10719398103.1]sec/[10083517582.8 ]sec/[10254451794.1]sec/[10033018813.5 sec]/[60548222298.0][3769572.305 55144411 337225 mVmK tKTKT tKtK tKtK tKKT evapratorofback evaporatorfromOutletevaporatortoInlet evaporatorfromOutlet ××+ ×−×+= ××+××− ××+××− ×−= −− −− Tetrahedral mesh was generated using (3262752) elements, (663589) nodes to empty cold store and (4475661) elements, (771219) nodes for loading cold store. 3. EXPERIMENTAL WORK Cold storage has been designed and constructed depends on the provided materials and equipment to achieve the freezing temperature below -20ºC. The outside and inside volumes of the cold store are 1m3 and 0.512m3 , respectively, as shown in figure (1-a). Hermetic sealed compressorsand air cooled condenser was located on the outside of the cold store. Force convection evaporator was put on the ceiling of the cold storage as shown in figure (1-b),this unit has two fans and the air velocity for each fan is 3.2m/s. After builds the cold store and before started the experimental work the temperature distribution in and out from evaporator has been measured as shown in figure (2).Also the other thermocouples are fixed at different levels, as shown in figure (3- a). These have the capability to monitor the temperature in case of empty store and in case of loaded store, see figure (3-a). The data are saved in SD card for the three 12 channel data logger that used in the present work. The work interested in monitoring the inside and outside temperature, and the relative humidity in the cold store. (a) (b) Figure (1): (a) cold storage and (b) The evaporator of the present design
  6. 6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME 128 Figure (2): Temperature in and out from the evaporator (a) (b) Figure (3): thermocouple distribution in three levels for empty cold store at (a) and loaded cold store at (b) 4. RESULTS AND DISCUSSION 4.1. Experimental results 4.1.1. Temperature distribution In the present work an experimental cold store was designed, built and operated to determine the spatial distribution of the air velocity and air temperature. Since the temperature distribution is a function of location and time, several cases have been implemented for temperature distribution for empty and loaded storage which can bedescribed as follows:
  7. 7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME 129 4.1.1.1. Empty cold store The air temperatures were determined at three levels located at different height ( 3cm, 28cm and 53cm) inside the cold store and at different storage temperatures, -2°C, -10°C, -20°C and -21°C respectively, as shown previously in figure (3-a). The air temperature was varied between-2.5°C and 2.8°C for -2°C storage temperature, - 10.9°C and -7.8°C for -10°C storage temperature, -21.1°C and -18.3°C for -20°C storage temperature, and -24.3°C and-20.1°C for -21°C storage temperature, respectively. In the case of storage temperature -21°C, the temperature inside the cold store was 32°C and the relative humidity was 32%. It takes 29 minutes to reach therequired storage temperature and then the system pause due to the presence order, ON-OFF thermostat. The operation started again when the temperature reached -17°C, due to differential temperature 4=∆T °C, and controlled by using the thermostat.The air temperature distributions are measured during the operation of the system for different runs. For each run the data are recorded by 12 channel data logger inside the cold store for 24 locations, six positions distributed in the center of each wall, as shown in figure (4-a), and 18 positions distributed in the air for three levels, as shown in figure (4-b). All temperatures are recorded with a 2 minute elapse time. (a) (b) Figure (4): The measured temperature distribution as a function of time in the cold store for storage temperature -21°C (a) 6 thermocouples distributed at the center of each wall. (b) 18 thermocouples distributed on three levels in the air. (See figure (3-a)) 4.1.1.2. Loaded cold store At the present work a 10.8 kg of meat, dimension 18cm×11cm×3cm, has been used and frozen at the cold store. As shown in figure (3-b) thermocouples are distributed and arranged on three levels within the loaded cold store. The air temperatures are measured at these three levels in the loaded cold store for different storage temperatures -20°C and 21°C, where the measured air temperatures are varied between -23.6°C and -20.5°C, for -20°C storage temperature, and -23.7°C and -22.3°C, for -21° C storage temperature, respectively. In the case of storage temperature -21°C, the temperature inside the cold store was 37°C and the relative humidity was 34%. Took the time to reach therequired storage temperature was 62.5 minutes.By using thermocouples and read the temperature by 12 channel data logger inside the cold store for 24 locations, six thermocouples are distributed in the center of each wall, as shown in figure (5-a), and 18 are distributed in the air for three levels during each test, as shown in figure (5-b). The temperature is recorded with 10 minutes time interval.
  8. 8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME 130 The temperature is recorded with 10 minutes time interval. Six parts (two for each level) of meat distributed in the left half of the store. Each part have 0.9kg, distributed in the three levels, inside the cold store, and the other half assumed symmetric to the left one, where (1M, 2M, 3M, 4M, 5M and 6M) referred to the locations of meat inside the cold store, see figure (3-b) . The thermocouples are inserted inside each part of the meat with (9cm×5.5cm×1.5cm) fixed locations. The initial temperature in the core of meat, at 1M, 2M, 3M, 4M, 5M and 6M locations, began from 33.9°C, 31.7°C, 34.8°C, 35.2°C, 31.8 °C and 36.5°C gradually. (a) (b) Figure (5): The measured temperature distribution as a function of time in the cold store for storage temperature -21°C (a) 6 thermocouples distributed at the center of each wall. (b) 18 thermocouples distributed on three levels in the air. (See figure (3-b)) 4.1.2. Air velocity The air velocity from the two fans is same in the evaporator, so the flow pattern is symmetrical in the cold store. Test make for finding the airflow distributions (Note that the points of airflow distribution are shown in figure (6-a)) inside empty cold store for local air velocity by using a hot wire anemometer, as shown in figure (7). The reason for non-uniform air temperature distributions is the bad spatial distribution of air velocity generated by evaporator fan. Each of velocities is normal to the six faces of parallelepiped of interest ),,,,( 212121 ZZyyXX VandVVVVV . The mean velocity V was then calculated using equation (12): )12()()()( 2 2 2 2 2 2 212121 LZZyyXX VVVVVV V +++ ++= The results from the equation above are shown in figure (6-b). The figures(6-b and 7) show the air velocity distributions are the best at the top level, due to exposure to the higher air velocity, and the best points in the lower level are (1,2 and 1M). Also, one can see from these figures the medium level has less airflow distributions and this explains the bad temperature distribution in this area.
  9. 9. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 ISSN 0976 – 6359(Online), Volume 5, Issue Figure (6): air velocity distribution (a), and Mean velocity distributionsby using a hot wire anemometer at (b) Figure (7): the airflow distributions for using a hot wire anemometer ((i) at x 4.2. Numerical results 4.2.1. Air flow and temperature distribution inside empty cold store for transient simulation The initial temperature inside the cold store was 30°C for Air at 25 °C. distributions, in a form of contours maps transient.It takes 4 hours and 52 minutes to reach below store.The air temperatures were determined at three levels located at different height, 5cm, 30cm and 55cm respectively inside the cold store, where three ZX figure (8-a, 8-b,8-c) and after accumulating time steps has been determined at different points, the locations of t the results of the temperature distribution at these points are shown in figure ( Three dimensional ε−K turbulent models are used to simulate the air distribution in the cold store. Figures (10-a, 10-b and 1 (10cm, 20cm and 30cm) respectively, inside the cold store.It is observed that the high velocity zones were concentrated between the ceiling fan, from the inlet with constan coils, at the back of the evaporator with constant velocity 1.78 m/s, and the approximation average air velocity at the top, medium and bottom levels are International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 6359(Online), Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME 131 air velocity distribution points for empty cold store by using a hot wire anemometer at y distributionsby using a hot wire anemometer at (b) the airflow distributions for the three levels in the cold storeand at different directions by using a hot wire anemometer ((i) at x-direction, (ii) at y-direction and (iii) at z distribution inside empty cold store for transient simulation The initial temperature inside the cold store was 30°C for Air at 25 °C. distributions, in a form of contours maps and charts, are presented in figures ( takes 4 hours and 52 minutes to reach below -21°C inside the simulation of cold The air temperatures were determined at three levels located at different height, 5cm, 30cm and spectively inside the cold store, where three ZX-planes are in the same locations, accumulating time steps equal to 30 minutes. The air temperature also has been determined at different points, the locations of these points are the same of figure ( temperature distribution at these points are shown in figure (9). turbulent models are used to simulate the air distribution in the 0-c) show as the velocity vectors in YZ-planes at different length (10cm, 20cm and 30cm) respectively, inside the cold store.It is observed that the high velocity zones were concentrated between the ceiling fan, from the inlet with constant velocity 3.2m/s, and cooling evaporator with constant velocity 1.78 m/s, and the approximation average air velocity at the top, medium and bottom levels are 0.55 m/s, 0.283 m/s and 0.303 International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), by using a hot wire anemometer at y distributionsby using a hot wire anemometer at (b) the three levels in the cold storeand at different directions by direction and (iii) at z-direction) distribution inside empty cold store for transient simulation The initial temperature inside the cold store was 30°C for Air at 25 °C. The temperature and charts, are presented in figures (8) and (9) with 21°C inside the simulation of cold The air temperatures were determined at three levels located at different height, 5cm, 30cm and planes are in the same locations, as shown in The air temperature also hese points are the same of figure (3-a) and turbulent models are used to simulate the air distribution in the planes at different length (10cm, 20cm and 30cm) respectively, inside the cold store.It is observed that the high velocity zones t velocity 3.2m/s, and cooling evaporator with constant velocity 1.78 m/s, and the approximation average m/s respectively.
  10. 10. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME 132 (a) (b) (c) Figure (8): Temperature distribution inside empty cold store at accumulate time step 30 minute located at: (a) top level, (b) medium level and (c) bottom level Figure (9): Air temperature distribution as a function of time in the cold store for 18 points distributed on three levels
  11. 11. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME 133 (a) (b) (c) Figure (10): velocity vectors distribution at different locations in YZ plane: ((a) at x=10cm, (b) at x=20cm and (c) at x=30cm) inside empty cold store 4.2.2. Airflow and air temperature distribution inside loaded cold store for steady state simulation The initial temperature inside the cold store was 35°C for Air at 25 °C, The temperature and airflow distribution in a form of contour maps are presented in figures (11) and (13) with steady state. It takes 370 iterations to reach whole cold store under -20°C inside the simulation of cold store. The air temperatures were determined at three levels located at different height (5cm, 30cm and 55cm ) inside the cold store, three ZX- planes at the same locations, as shown in figures (11-a,11-b and 11-c). The Air velocity vector distribution also has been determined at different length in a form of YZ-planes at the same locations, as shown in figures (12-a, 12-b and 12-c). It is observed that the high velocity zones were concentrated between the ceiling fan, from the inlet with constant velocity 3.2m/s, and cooling coils, at the back of the evaporator with constant velocity 1.78 m/s. The approximation of the average air velocity at the top, medium and bottom levels are 0.603 m/s, 0.377 m/s and 0.366 m/s respectively.
  12. 12. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME 134 (a) (b) (c) Figure (11): Temperature distribution inside loaded cold store located at (a) top level, (b) medium level and (c) bottom level (a) (b) (c) Figure (12): velocity vectors distribution at different locations at YZ- plane: ((a) at x=10cm, (b) at x=20cm and (c) at x=30cm) inside empty cold store
  13. 13. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME 135 4.3. Comparison between experimental and numerical results Temperature and air flow distribution inside empty cold store The temperature distribution results in the three levels (bottom, medium and top) for empty cold store as shown in the figures (13-i, 13-ii and 13-iii) respectively. Average of the relative error between experimental and numerical air temperature distribution is equal to 13%. Air flow distribution results in the three levels (bottom, medium and top) for empty cold store as shown in the figure (14) with relative error between experimentally and numerically equal to 20%. (i) (ii) (iii) Figure (13): Comparison between experimental and numerical for air temperature distribution inside empty cold store: (i) Bottom level, (ii) Medium level and (iii) top level
  14. 14. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME 136 Figure (14): Comparison between experimental and numerical for air velocity distribution inside empty cold store: (i) Numerical and (ii) Experimental 4.4. CONCLUSIONS From the present work results for the airflow and temperature distribution in a cold store, different distinguish conclusions have been pointed out: 1- From the analysis of the variation of the air velocity at the middle and bottom of the cold store, it was found that the variation is less than the top level of cold store because the evaporator was placed at the top level of cold store. 2- The numerical results show the average air velocity for empty cold store at the top, medium and bottom levels are 0.55 m/s, 0.283 m/s and 0.303 m/s respectively. Also, they show the average air velocity for loading cold store at the top, medium and bottom levels 0.603 m/s, 0.377 m/s and 0.366 m/s respectively. 3- The air velocity strongly influences the performance of the unit. If the air velocity is too low the necessary refrigerating effect and the correct storage temperature cannot be guaranteed. If air velocity is too high the air stream becomes more turbulent thus increasing heat transfer with the environment and the correct storage temperature can be guaranteed. 4- The two fans operate in normal conditions and therefore, the flow pattern is symmetrical inside the cold store. 5- The air stacks appeared inside empty and loaded cold storage in several points; first stack introduced should be close to the evaporator with minimum and maximum velocity equal to 0.038 m/sec and 0.431 m/sec for empty cold store, 0.08m/sec and 0.587 m/sec for loading cold store respectively. Other stack appeared two more in empty store and four more in loaded store with minimum and maximum velocity range equal to 0.025 m/sec and 0.46 m/sec for empty store, 0.019 m/sec and 0.718 m/sec for loading store respectively. REFERENCE [1] Roy J. Dossat, "Principle of Refrigeration", second Edition, John Wiley and sons, 1981. [2] M.L. Hoang et al ,"Analysis of the air flow in a cold store by means of computational fluid dynamics", International Journal of Refrigeration, vol. 23 No. 2, pp. 127-140, 2000. [3] H.B. Nahor, M.L. Hoang, P. Verboven,"CFD model of the airflow, heat and mass transfer in cool stores", International Journal of Refrigeration, Vol. 28, Issue 3, pp. 368–380, 2005. [4] SERAP AKDEMIR and SELCUK ARIN,"Spatial Variabilty of Ambient Temperature, Relative Humidity and Air velocity in a Cold Store", Journal of Central European Agriculture, vol. 7, No.1, pp. 101-110, 2006.
  15. 15. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 123-137 © IAEME 137 [5] Bjorn Margeirsson and Sigurjon Arason, "Temperature monitoring and CFD modelling of a cold storage", Ph.D. Thesis, University of Iceland, 2008. [6] Seyed Majid Sajadiye, Hojat Ahmadi, Seyed Mostafa Hosseinalipour, Seyed Saeid Mohtasebi, Mohammad Layeghi, Younes Mostofi, Amir Raja, "Evaluation of a Cooling Performance of a Typical Full Loaded Cool Storage Using Mono-scale CFD Simulation", Vol. 6, No. 1, 2012. [7] ANSYS CFX Help (2012), Turbulence and Wall Function Theory, Two Equation Turbulence Models, Release 14.5. [8] Jones W. P. and Launders B. E., "The Predicition of Laminarization with a Two-Equation Model of Turbulence", Int. J. Heat and Mass Transfer 15, 301-314, 1972. [9] Gunwant D.Shelake, Harshal K. chavan, Prof. R. R. Deshmukh and Dr. S. D. Deshmukh, “Model for Prediction of Temperature Distribution in Workpiece for Surface Grinding using FEA”, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 3, Issue 2, 2012, pp. 207 - 213, ISSN Print: 0976-6480, ISSN Online: 0976-6499. [10] Ambeprasad S. Kushwaha, Dhiraj K. Patil, Vinaykumar J. Pandey, Sandeepkumar K. Yadav and Tushar S. Suryawanshi, “Thermal Analysis of Heat Sink (Variable Shield Profile) Used in Electronic Cooling using CFD Analysis”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 5, Issue 3, 2014, pp. 114 - 121, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. [11] N.S.Venkatesh Kumar and Prof. K. Hema Chandra Reddy, “CFD Investigation of Ceiling Shape on Airflow Distribution for a Generic 2-D Room Model with and Without Passive Control”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 5, Issue 1, 2014, pp. 10 - 25, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.

×