Performance evaluation of a solar assisted heat pump drying system

PERFORMANCE EVALUATION OF A SOLAR ASSISTED HEAT PUMP DRYING SYSTEM SHEK MOHAMMOD ATIQURE RAHMAN NATIONAL UNIVERSITY OF SINGAPORE 2003 PERFORMANCE EVALUATION OF A SOLAR ASSISTED HEAT PUMP DRYING SYSTEM Founded 1905 SUBMITTED BY SHEK MOHAMMOD ATIQURE RAHMAN (B.Sc.Eng.,BUET.) A THESIS SUBMITTED FOR THE DEGREE OF MASTER OF ENGINEERING DEPARTMENT OF MECHANICAL ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2003 Acknowledgements ACKNOWLEDGEMENTS For the successful completion of the project, firstly, the author would like to express his gratitude toward Almighty Allah for his blessing and mercy The author would like to express his profound thanks and gratitude to his project supervisor Associate Professor M.N.A Hawlader for giving an opportunity to work under his guidance, advice, and patience throughout the project In particular, necessary suggestions and recommendations of project supervisor for the successful completion of this research work have been invaluable The author is also grateful to his colleague Mr Jahangeer for his active co-operation and valuable advice throughout the project The author extends his thanks to all the technical staffs in the thermal division, particularly Yeo Khee Ho, Hung-Ang Yan Leng, Low Kim Tee Desmond, Tan Tiong Thiam, Anwar Sadat and Roselina Abdullah for their assistance during the fabrication of test rig and performance of experiments The author expresses his heartfelt thanks to all of his friends who have provided inspiration for the completion of project Finally, the author extends his gratitude to his parents, wife, daughter and other family members for their patience and support throughout this work The author would like to acknowledge the financial support for this project provided by the National University of Singapore in the form of Research Scholarship i Table of Contents TABLE OF CONTENTS Page ACKNOWLEDGEMENTS i TABLE OF CONTENTS ii SUMMARY vi NOMENCLATURE ix LIST OF FIGURES xi LIST OF TABLES xv CHAPTER INTRODUCTION 1.1 Open Air Sun Drying 1.2 Indirect Solar Drying 1.3 Heat Pump Drying 1.4 Solar Assisted Heat Pump Drying CHAPTER LITERATURE REVIEW CHAPTER EXPERIMENTS 17 3.1 Description of the Setup 17 3.1.1 Air flow path 18 3.1.2 Refrigerant flow path 19 3.2 Selection of Components 21 3.2.1 21 Evaporator -collector ii Table of Contents CHAPTER CHAPTER 3.2.2 Compressor 23 3.2.3 Air-cooled condenser 24 3.2.4 Water-cooled condenser 24 3.2.5 Thermostatic expansion valve 25 3.2.6 Air collector 25 3.2.7 Blower 26 3.2.8 Electric heater 26 3.2.9 Dryer 26 3.2.10 Evaporator/de-humidifier 27 3.3 Instrumentation 27 3.4 Experimental Procedure 29 3.5 Drying Test 30 3.6 Collector Test 32 3.7 Error Analysis 32 LOCAL METEOROLOGICAL DATA 36 4.1 Climatic Condition of Singapore 36 4.2 Model for Meteorological Data for Singapore 38 SIMULATION AND OPTIMIZATION 43 Simualtion 43 5.1.1 43 5.1 Simualtion Methodology iii Table of Contents 5.2 CHAPTER 48 5.2.1 Economic analysis 48 5.2.2 Economic evaluation methodology 53 RESULTS AND DISCUSSION 56 6.1 Experimental Results 56 6.1.1 Drying characteristics 56 6.1.2 Performance parameters 72 6.2 Comparison Between Experimental and Simulation Results 88 6.3 CHAPTER Optimisation 6.2.1 Product temperature 88 6.2.2 Moisture content 89 6.2.3 Co-efficient of performance (COP) 90 6.2.4 Collector efficiency 92 6.2.5 Solar fraction (SF) 94 Cost Analysis of the System 96 6.3.1 Pay back period of the system 96 6.3.2 Optimum variables 99 CONCLUSIONS 101 RECOMMENDATIONS 104 REFERENCES 105 iv Table of Contents APPENDIX A Calibration Graph 114 APPENDIX B Experimental and Simulation results 118 v Summary SUMMARY Most agricultural products contain a high percentage of water and, therefore, considered highly perishable Losses of agricultural product in developing countries are significantly higher The post-harvest losses of agricultural products can be reduced drastically by using proper drying technique Product quality and energy requirement are very important considerations in drying technology Singapore is a country of abundant solar irradiation and high ambient temperature throughout the year For this meteorological condition, a solar assisted heat pump drying system was designed, fabricated, and tested The dryer, in the present study, is used to analyse the drying characteristics of the food grains The drying chamber is scaled down in size to make it convenient to carry out the drying experiment by limiting the quantity of drying material In actual situation, this drying chamber can be scaled up to dry higher quantity of material An hourly energy analysis is carried out to examine the amount of energy that can be derived from the system This energy analysis can be used to perform a scale-up of the drying chamber The system mainly comprises a compressor, water condenser, evaporator-collector, thermostatic expansion valve, air collector, auxiliary heater, drying chamber, dehumidifier, and blower There are two distinct paths, the air and the refrigerant R134a, to transport energy from one location to another Two evaporators, fitted in parallel mode, are used in the heat pump circuit, one acting as a dehumidifier and the other as a solar collector Once the air from the dryer exit has passed through the dehumidifier, it enters an air collector, absorbs solar energy and transfers it to the drying medium leading to an increase in temperature Additional heating is provided at vi Summary the condenser and, if necessary, at the auxiliary heater to achieve the desired condition A data acquisition system is used to record and monitor different parameters required for the evaluation of the system performance A series of experiments were conducted at wide range of operating conditions by using different agricultural food grains under the meteorological conditions of Singapore The experiments consist of drying of green beans, paddy, and grams with the careful examination of its drying characteristic while monitoring the performance of the key components like solar collectors, dehumidifier and condensers On the analysis of drying characteristics of the food grains, the three principle process parameters are considered: drying air temperature, airflow rate and the effect of dehumidification A series of drying characteristics curve have been plotted to examine the effect of these parameters on the drying time The nature of the drying rate and diffusivity of the above three materials are also examined The collector is one of the most important components in a solar drying system To investigate the performance of evaporatorcollector and air collector, tests were conducted according to the ASHRE standard For the evaluation of performance of the system, solar fraction (SF) and coefficient of performance (COP) are considered Experimental results were analysed and, finally, compared with simulation results Good agreement was found between simulation and experimental results, as stated in the results and discussion section of this thesis The diffusion co-efficient of green beans, paddy and grams, for the conditions considered, were found to be 9.61x10-11 m2/sec, 1.075x10-10 m2/sec, 1.08x10-10 m2/sec, respectively The range of efficiency of air collector, with and without dehumidifier, was found to be between 0.72 - 0.76 and 0.42 - 0.48, respectively Maximum vii Summary evaporator collector efficiency of 0.87 against a maximum air collector efficiency of 0.76 was obtained A series of numerical simulations were performed for different operating condition to optimise the system, especially to optimise the evaporator-collector and air collector area, on the basis of drying load Each batch of drying included 100 kg of food grams An economic analysis of the system was carried out to determine the minimum payback period The optimum values of air collector area, evaporator collector area, drying temperature, and air mass flow rate were found of about 1.25 m2, m2, 500C, and 0.036 kg/sec, respectively, which provided around 89% of the total load From the economic analysis of the system, it was found that the system has a significant potential to provide sufficient return on investment for the life cycle of the system, with minimum payback period of about 4.37 years viii Appendix B 130.00 135.00 140.00 145.00 150.00 155.00 160.00 165.00 170.00 175.00 180.00 185.00 190.00 195.00 200.00 205.00 210.00 215.00 220.00 225.00 230.00 49.58 49.97 50.66 51.02 51.22 52.04 50.85 50.94 51.26 51.95 51.67 50.58 49.72 50.23 50.50 51.19 51.37 50.48 49.92 50.09 50.66 38.09 38.20 38.36 38.84 39.03 39.41 39.64 39.57 40.01 40.14 40.42 40.55 40.55 40.61 40.74 40.94 41.07 41.07 40.94 41.68 41.29 Table B4 Experimental results for Figure 6.7 and 6.8 (Different drying temperature for paddy and grams are 550C & 450C, Constant air mass flow rate 0.06kg/sec) Time 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 Paddy Paddy Grams Grams Moisture Moisture Moisture Moisture Content%(db) Content%(db) Content%(db) Content%(db) (55C, 06kg/sec) (55C, 036kg/sec) (55C, 06kg/sec) (55C, 036kg/sec 40.72 41.03 39.62 41.16 39.26 40.59 38.86 40.79 38.02 39.98 37.55 39.87 36.28 39.06 36.53 38.88 35.11 38.57 35.49 37.6 34.41 37.88 34.12 36.34 33.18 37.07 33.23 35.62 32.12 36.71 32.37 34.86 31.27 36.3 31.28 34.01 30.71 35.41 30.62 33.31 29.56 34.98 29.38 32.98 28.54 34.43 29.07 32.17 27.63 33.47 28.56 31.85 26.41 32.69 28.04 31.3 25.31 31.67 27.42 31.1 24.32 30.77 27.02 30.76 23.54 29.88 26.4 30.43 121 Appendix B 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 22.61 22.14 21.63 21.28 20.84 19.93 19.37 18.99 18.48 17.89 17.3 17.01 16.7 16.31 16.02 15.84 15.55 15.15 14.85 14.45 14.02 13.74 13.36 12.88 12.23 11.83 11.45 11.23 39.18 28.56 27.95 27.26 26.88 26.31 25.83 25.06 24.71 24.3 23.92 23.35 22.36 21.88 21.33 21.01 20.63 20.22 19.94 19.4 19.1 18.75 18.46 18.01 17.59 17.19 16.76 16.22 25.83 25.12 24.65 23.89 23.32 22.86 22.45 21.94 21.38 20.88 20.31 19.75 19.21 18.73 18.05 17.62 17.13 16.61 16.11 15.65 15.01 14.65 14.05 13.65 13.11 12.56 12.02 11.68 30.09 29.64 29.14 28.77 28.17 27.76 27.34 26.85 26.37 25.75 25.24 24.75 24.11 23.57 23.01 22.6 22.12 21.79 21.17 20.8 20.43 19.98 19.45 18.94 18.45 17.95 17.55 17.02 Table B5 Experimental results for Figure 6.9 and 6.10 (Different air mass flow rate green beans and grams are 0.036kg/sec & 0.06kg/sec Constant drying temperature 550C) Time 10 15 20 25 30 35 40 50 Green beans Green beans Grams Grams Moisture Moisture Moisture Moisture Content%(db) Content%(db) Content%(db) Content%(db) (55C, 036kg/sec) (55C, 06kg/sec) (55C, 06kg/se) (55C, 036kg/sec) 38.73 38.73 39.23 40.39 37.88 36.65 38.65 38.75 37.42 35.08 36.94 37.53 37.03 34.64 36.23 36.85 36.18 32.77 35.69 35.18 35.33 31.61 34.49 34.57 34.54 30.93 33.78 34.04 33.64 30.20 32.82 33.77 32.79 29.43 31.69 33.12 31.94 28.23 30.16 32.71 122 Appendix B 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 31.1 29.84 29.4 29.4 28.94 28.55 27.71 26.86 26.54 26.01 25.16 24.86 24.32 23.95 23.47 23.02 22.87 22.62 22.23 21.97 21.65 21.26 20.92 20.08 19.75 19.23 19.23 19.02 18.75 18.52 18.38 18.23 18.01 17.87 17.72 17.64 27.90 27.31 26.44 26.01 25.29 24.72 24.22 23.58 23.14 22.81 22.46 21.67 21.20 21.06 20.39 20.62 20.76 19.66 19.79 19.42 18.65 19.00 18.27 18.06 17.89 17.30 17.13 17.28 16.53 16.47 16.43 15.81 16.06 15.68 15.55 15.36 29.34 28.88 27.48 26.55 25.85 24.79 23.92 22.55 22.01 21.52 21.08 20.75 20.19 19.65 19.12 18.71 18.21 17.85 17.35 16.95 16.45 32.19 31.43 30.64 29.81 28.49 27.68 27.14 26.72 26.12 25.65 24.92 24.31 23.88 22.71 22.08 21.74 21.16 20.62 20.02 19.64 19.23 Table B6 Experimental results for Figure 6.11 and 6.12 (Drying condition for grams and green beans are 55C, 0.06kg/sec & 45C, 0.06kg/sec) Time Green beans Moisture Content%(db) (With dehumidifier) 38.725 Green beans Moisture Content%(db) (Without dehumidifier) 38.92 Grams Moisture Content%(db) (With dehumidifier) 39.62 Grams Moisture Content%(db) (Without dehumidifier) 39.23 123 Appendix B 10 15 20 25 30 35 40 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 38.725 37.878 37.03 35.335 35.335 33.639 33.639 32.792 31.944 31.096 30.249 30.249 29.401 29.401 28.554 27.706 26.858 26.858 26.858 25.163 25.163 24.315 23.468 23.01 22.62 22.32 22.01 21.772 21.58 21.25 20.925 20.64 20.34 20.12 20.077 19.87 19.65 19.45 19.23 18.95 18.65 18.32 18.05 17.75 17.45 37.33 36.22 34.63 33.69 32.16 31.46 29.82 29.08 28.09 27.38 26.15 25.51 24.39 23.72 22.65 22.54 21.35 20.74 19.93 19.47 19.08 18.35 17.94 17.19 38.86 37.55 36.53 35.49 34.12 33.23 32.37 31.28 29.38 29.07 28.28 27.42 27.02 26.4 25.83 25.01 24.22 23.43 22.96 22.54 21.94 21.38 20.01 19.43 18.83 18.02 17.62 17.13 16.51 16.01 15.65 15.11 14.65 14.01 38.65 36.94 36.23 35.69 34.49 33.78 32.82 31.69 30.16 29.34 28.88 27.48 26.55 25.85 24.79 23.92 22.55 22.01 21.52 21.08 20.75 20.35 20.01 19.77 19.53 19.11 18.84 18.54 18.12 17.88 17.65 17.35 17.15 17.01 124 Appendix B Table B7 Experimental results for Figure 6.13 and 6.16 (Material Paddy: 45C, 0.06kg/sec, With dehumidifier, L=6mm) Time 20 40 60 80 100 120 140 160 180 200 220 240 Mass gm 1206.34 1174.82 1154.73 1136.84 1109.32 1093.39 1075.67 1057.78 1043.08 1025.93 1013.27 1004.36 985.41 Moisture content%(db) 41.03 37.34 34.01 30.99 28.35 26.02 23.98 22.12 20.45 19.01 17.56 16.3 15.19 Drying rate g/g dry Log(w/wo) t/L2 0.0044 0.0043 0.0043 0.0041 0.0040 0.0038 0.0037 0.0036 0.0034 0.0036 0.0034 0.0032 -0.04093 -0.08149 -0.12188 -0.16055 -0.19779 -0.23325 -0.26832 -0.30241 -0.33412 -0.36858 -0.40091 -0.43154 0.56 1.11 1.67 2.22 2.78 3.33 3.89 4.44 5.00 5.56 6.11 6.67 Table B8 Experimental results for Figure 6.14 and 6.17 (Material Grams: 55C, 0.036kg/sec, Without dehumidifier, L=6mm) Time 20 40 60 80 100 120 140 160 180 200 220 240 Mass gm 1247.12 1219.56 1193.34 1172.02 1144.9 1113.46 1100.47 1084.3 1068.29 1042.89 1025.89 1016.43 1008.02 Moisture content%(db) 41.02 37.15 33.7 30.75 28.12 25.89 23.98 22.22 20.65 19.23 17.98 16.85 15.8 Drying rate Log(w/wo) g/g dry 0.0046 0.0045 0.0043 0.0041 0.0038 0.0036 0.0035 0.0034 0.0033 0.0031 0.0030 0.0029 -0.04304 -0.08537 -0.12515 -0.16398 -0.19986 -0.23315 -0.26625 -0.29808 -0.32902 -0.35821 -0.3864 -0.41434 t/L2 0.56 1.11 1.67 2.22 2.78 3.33 3.89 4.44 5.00 5.56 6.11 6.67 Table B9 Experimental results for Figure 6.15 and 6.18 (Material Green beans: 45C, 0.06kg/sec, Without dehumidifier, L=6mm) Time 20 Mass gm 1235.7 1205.86 Moisture content%(db) 38.73 35.35 Drying rate g/g dry Log(w/wo) 0.0043 -0.03966 t/L2 0.56 125 Appendix B 40 60 80 100 120 140 160 180 200 220 1176.03 1146.19 1123.81 1108.89 1086.52 1076.06 1064.14 1049.22 1041.76 1041.76 32.39 29.95 27.7 25.75 23.75 22.01 20.65 19.45 18.25 17.53 0.0041 0.0037 0.0036 0.0034 0.0037 0.0035 0.0030 0.0028 0.0029 0.0019 -0.10406 -0.13808 -0.172 -0.2037 -0.23881 -0.27186 -0.29956 -0.32556 -0.35321 -0.37069 1.11 1.67 2.22 2.78 3.33 3.89 4.44 5.00 5.56 6.11 Table B10 Experimental results for Figure 6.19, 6.25 and 6.28 Time Radiation W/m2 Air collector efficiency 11 11.25 11.5 11.75 12 12.25 12.5 12.75 13 13.25 13.5 846.95 875.87 889.87 895.54 934.47 942.42 932.48 920.24 934.43 943.47 920.54 0.73 0.71 0.73 0.75 0.75 0.71 0.72 0.74 0.75 0.74 0.71 Evaporatorcollector Efficiency 0.86 0.87 0.87 0.87 0.86 0.86 0.86 0.85 0.85 0.84 0.85 Table B11 Experimental results for Figure 6.20 Time 11 11.25 11.5 11.75 12 12.25 12.5 12.75 13 13.25 13.5 Air collector efficiency Air mass flow rate 0.06 kg/sec 0.72 0.73 0.76 0.74 0.75 0.76 0.77 0.76 0.75 0.76 0.74 Air collector efficiency Air mass flow rate 0.036 kg/sec 0.69 0.71 0.73 0.72 0.73 0.71 0.72 0.74 0.73 0.74 0.71 126 Appendix B Table B12 Experimental results for Figure 6.21 and 6.23 Time Air collector Air collector Air collector inlet Air collector inlet Ambient 0 efficiency efficiency temperature( C) temperature ( C) temperature with without with without ( 0C) dehumidifier dehumidifier dehumidifier dehumidifier 11 0.71 0.33 28.08 35.08 35.4 11.25 0.72 0.39 28.31 35.31 31.8 11.5 0.76 0.39 28.46 35.46 32.8 11.75 0.74 0.47 28.6 35.6 35.6 12 0.75 0.46 28.65 35.65 34.9 12.25 0.76 0.48 29.02 36.02 34.7 12.5 0.77 0.5 29.21 36.21 33.3 12.75 0.76 0.46 29.71 36.71 36.54 13 0.75 0.49 28.52 35.52 35 13.25 0.77 0.56 29.09 36.09 34.4 13.5 0.72 0.45 28.89 35.89 33.8 13.75 0.75 0.36 27.58 34.58 32.8 Table B13 Experimental results for Figure 6.22, 6.24, 6.27 and 6.30 Air collector (Tfi-Ta)/It Air collector (Tfi-Ta)/It Evaporator- (Tfi-Ta)/It efficiency with efficiency without collector with dehumidifier without dehumidifier efficiency dehumidifier dehumidifier 0.75 -0.008 0.76 0.001 0.78 -0.0034 0.75 -0.011 0.75 0.0025 0.79 -0.004 0.78 -0.009 0.72 0.01 0.83 -0.0075 0.77 -0.0069 0.715 0.012 0.81 -0.0033 0.79 -0.0118 0.71 0.013 0.82 -0.0044 0.79 -0.0141 0.705 0.014 0.83 -0.0069 0.78 -0.0089 0.84 -0.006 0.78 -0.009 0.83 -0.0053 0.78 -0.0092 0.82 -0.005 0.79 -0.0107 0.84 -0.0078 0.8 -0.0093 0.79 -0.0063 Table B14 Experimental results for Figure 6.29 127 Appendix B Time Air temperature (min) at the inlet of air collector 26.3 26.1 26.5 26.4 26.2 26.3 26.5 26.1 26.2 26.3 11 11.3 12 12.3 13 13.3 14 14.3 15 15.3 Refrigerant temperature at the inlet of evaporator-collector 10.62 10.3 11.15 11.01 10.75 10.56 10.33 11.28 10.43 9.91 Table B15 Experimental results for Figure 6.26 Time 26.66 53.32 79.98 106.64 133.3 159.96 186.62 213.28 239.94 Evaporatorcollector efficiency Speed (1800 RPM) 0.832 0.865 0.856 0.835 0.868 0.825 0.852 0.854 0.838 0.832 Evaporatorcollector efficiency Speed (1200 RPM) 0.805 0.808 0.816 0.805 0.78 0.772 0.805 0.816 0.742 0.736 Table B16 Experimental results for Figure 6.31 and 6.34 Time Radiation Coefficient of W/m2 10 20 30 922.36 957.87 939.26 954.87 performance COP 5.46 5.45 5.56 5.57 Time 30 60 90 120 Radiation W/m2 992.63 906.97 942.56 910.46 942.59 Solar fraction SF 0.68 0.74 0.76 0.79 0.82 128 Appendix B 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 954.87 945.87 965.45 960.76 968.45 970.23 935.67 965.45 932.91 955.84 954.65 934.46 945.62 935.45 925.65 945.87 950.37 939.82 927.36 920.83 916.26 910.27 5.68 5.70 5.70 5.66 5.69 5.65 5.55 5.43 5.54 5.49 5.47 5.43 5.42 5.41 5.51 5.52 5.54 5.54 5.52 5.48 5.42 5.41 150 180 210 240 270 810.52 835.62 774.26 652.4 632.61 0.80 0.81 0.72 0.67 0.66 Table B17 Experimental results for Figure 6.32 and 6.33 Time 10 20 30 40 50 60 70 80 90 100 110 120 130 Coefficient of performance (COP) Compressor speed 1200 rpm 5.46 5.45 5.56 5.57 5.68 5.70 5.70 5.66 5.69 5.65 5.55 5.43 5.54 5.49 Coefficient of performance (COP) Compressor speed 1800 rpm 4.90 4.92 4.93 4.93 4.94 4.94 4.95 4.94 4.98 5.00 5.00 5.00 4.99 5.00 Coefficient of performance (COP) Air mass flow rate 0.06 kg /sec 5.46 5.45 5.56 5.57 5.68 5.70 5.70 5.66 5.69 5.65 5.55 5.43 5.54 5.49 Coefficient of performance (COP) Air mass flow rate 0.048 kg /sec 4.97 4.98 4.98 4.97 5.01 5.02 5.00 4.98 4.88 4.92 4.96 4.95 4.88 4.75 129 Appendix B 140 150 160 170 180 190 200 210 220 230 240 250 5.47 5.43 5.42 5.41 5.51 5.52 5.54 5.54 5.52 5.48 5.42 5.41 5.02 5.03 5.06 4.99 5.01 5.00 4.97 5.01 5.00 5.06 5.09 5.09 5.47 5.43 5.42 5.41 5.51 5.52 5.54 5.54 5.52 5.48 5.42 5.41 4.79 4.85 4.92 4.88 4.81 4.77 4.68 4.63 4.60 4.62 4.65 4.66 Table B18 Experimental results for Figure 3.35 and 3.36 Time Solar Fraction(SF) 500C 30 60 90 120 120 150 180 210 240 0.79 0.83 0.85 0.96 0.94 0.92 0.91 0.88 0.86 0.85 Solar Fraction(SF) Solar Fraction(SF) Solar Fraction(SF) 550C 0.67 0.63 0.73 0.75 0.77 0.78 0.69 0.62 0.59 0.56 Air mass flow rate Air mass flow rate 036 kg/sec 048 kg/sec 0.68 0.67 0.74 0.63 0.76 0.73 0.79 0.75 0.81 0.77 0.8 0.78 0.81 0.69 0.72 0.62 0.67 0.59 0.66 0.56 Table B19 Experimental results for Figure 3.37 Time 30 60 90 120 150 180 Solar Fraction(SF) Solar Fraction(SF) Air mass flow rate Air mass flow rate Compressor speed Compressor speed 1200 rpm 1800 rpm 0.69 0.68 0.77 0.74 0.78 0.76 0.83 0.79 0.84 0.81 0.86 0.8 0.9 0.82 130 Appendix B 210 240 270 0.83 0.81 0.79 0.72 0.67 0.66 Comparison Table B20 Comparison between simulation and experimental results for Figure 6.38 Time Drying Temperature C Simulation 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 12 18 30 42 48 60 72 78 90 102 108 120 132 138 150 162 168 180 192 198 210 222 228 240 252 258 270 Product Temperature C (Green beans) Simulation 31.6 31.21 32.36 33.45 34.49 35.48 36.41 37.3 38.14 38.94 39.69 40.4 41.07 41.71 42.3 42.86 43.39 43.88 44.35 44.78 45.19 45.57 45.93 46.26 46.58 46.87 47.14 47.39 Product Temperature C (Green beans) Experiment 31.6 31.9 31.58 32.6 32.6 32.4 35.2 34.25 36.25 35.9 36.2 39.5 39.8 39.98 40.25 40.98 41.25 41.26 42.3 42.58 42.69 44.69 44.98 44.96 44.58 45.9 46.8 46.98 Table B21 Comparison between simulation and experimental results for Figure 6.39 and 6.40 (Material: Green beans) 131 Appendix B Time 12 18 30 42 48 60 72 78 90 102 108 120 132 138 150 162 168 180 192 198 210 222 228 240 Moisture Moisture Moisture Moisture Content %(db) Content %(db) Content% (db) Content %(db) Simulation Experiment Simulation Experiment (55C, 048kg/sec) (55C, 048kg/sec) (45C, 06kg/sec) (45C, 06kg/sec) 38.73 38.73 37.66 37.87 34.94 35.08 34.81 35.33 32.69 32.77 32.68 33.64 30.32 30.92 31.34 32.79 28.32 29.42 29.58 31.09 26.28 27.89 28.71 30.24 24.47 26.44 27.46 29.41 23.19 25.29 25.86 27.71 21.78 24.21 24.93 26.85 22.07 23.58 24.29 25.46 20.98 22.8 22.75 24.31 19.53 21.67 21.52 23.46 18.44 21.06 20.35 22.62 17.85 20.62 20.64 21.77 17.11 19.66 20.23 21.32 18.72 19.41 19.52 20.92 18.27 18.99 18.86 20.07 16.89 18.06 17.63 19.23 16.5 17.29 17.13 18.87 16.7 17.28 16.93 18.38 15.73 16.46 16.35 18.12 15.28 15.8 16.48 17.92 15.06 15.67 16.35 17.74 14.43 15.35 16.13 17.54 14.29 15.06 15.58 17.23 Table B22 Comparison between simulation and experimental results for Figure 6.41 and 6.42 Time 26.66 53.32 79.98 106.64 133.3 Coefficient of performance (COP) Simulation 6.01 6.12 6.02 6.68 6.65 6.23 Coefficient of performance (COP) Experiment 5.65 5.98 5.65 6.35 6.45 6.02 Coefficient of performance (COP) Simulation 5.31 5.41 5.22 5.98 5.96 5.61 Coefficient of performance (COP) Experiment 5.1 5.1 5.05 5.6 5.65 5.5 132 Appendix B 159.96 186.62 213.28 239.94 6.12 6.01 5.25 5.23 5.95 5.56 4.98 4.95 5.32 5.23 5.18 5.31 4.98 4.97 4.98 5.1 Table B23 Comparison between simulation and experimental results for Figure 6.43 and 6.44 Time 26.66 53.32 79.98 106.64 133.3 159.96 186.62 213.28 239.94 Evaporator- Evaporator- Evaporator- EvaporatorCollector Collector Collector Collector efficiency efficiency efficiency efficiency Simulation Experiment Simulation Experiment 0.841 0.832 0.816 0.805 0.875 0.865 0.814 0.808 0.864 0.856 0.822 0.816 0.842 0.835 0.815 0.805 0.871 0.868 0.801 0.791 0.834 0.825 0.807 0.795 0.862 0.852 0.821 0.805 0.859 0.854 0.823 0.816 0.839 0.838 0.814 0.802 0.858 0.832 0.825 0.813 Table B24 Comparison between simulation and experimental results for Figure 6.45 and 6.46 Time 26.66 53.32 79.98 106.64 133.3 159.96 186.62 213.28 239.94 Solar fraction(SF) Simulation 0.95 0.96 0.78 1 0.89 0.92 0.89 Solar fraction(SF) Experiment 0.92 0.94 0.76 1 0.87 0.98 0.88 0.88 Solar fraction(SF) Simulation 0.37 0.38 0.47 0.52 0.65 0.63 0.81 0.57 0.58 0.57 Solar fraction(SF) Experiment 0.33 0.35 0.43 0.51 0.64 0.6 0.81 0.56 0.57 0.57 133 Appendix B Results of Economic analysis Table B25 Simulation results for Figure 6.47 and 6.48 (Pay back period for different air collector area, Discount rate = 0.07, Inflation rate=0.13) Evaporator- Temperature Mass Air flow rate collector collector of air area area 0.036 m2 m2 C kg/sec 0.15 0.5 0.75 1.25 1.5 2 2 2 2 50 50 50 50 50 50 50 0.036 0.036 0.036 0.036 0.036 0.036 0.036 Material Weight Material Weight Material Weight 100kg 75 kg 50 kg Pay back Pay back Pay back period(yrs) period(yrs) period(yrs) 5.31 6.65 9.4 4.74 5.95 8.48 4.5 5.64 4.38 5.52 7.88 4.37 5.5 7.87 4.39 5.53 7.94 4.48 5.66 8.09 Table B26 Simulation results for Figure 6.49 (Pay back period for different air collector area, Discount rate = 0.07, Material weight=100kg) Inflation rate Evaporator- Temperature Mass Air flow rate collector collector area area of air 0.11 0.13 0.16 m2 m2 C kg/sec Pay back Pay back Pay back period period period 0.15 50 0.036 5.47 5.31 5.06 0.5 50 0.036 4.9 4.74 4.54 0.75 50 0.036 4.66 4.5 4.46 50 0.036 4.54 4.38 4.21 1.25 50 0.036 4.53 4.37 4.2 1.5 50 0.036 4.55 4.39 4.22 2 50 0.036 4.64 4.48 4.31 134 Appendix B Table B27 Simulation results for Figure 6.50 (Pay back period for different air collector area, Inflation rate = 0.03, Material weight=100kg) Discount rate Evaporator- Temperature Mass Air flow rate collector collector area area of air 0.05 0.07 m2 m2 C kg/sec Pay back Pay back period period 0.15 50 0.036 6.18 5.31 0.5 50 0.036 5.61 4.74 0.75 50 0.036 5.37 4.5 50 0.036 5.25 4.38 1.25 50 0.036 5.24 4.37 1.5 50 0.036 5.26 4.39 2 50 0.036 5.35 4.48 0.1 Pay back period 3.53 3.45 3.24 3.23 3.25 3.35 135 [...]... a solar assisted heat- pump system to supply heat for industrial processes in the range 1000C to 1300C He showed that the system was economically superior to electrical heating and solar only systems, and was competitive with fuel burning systems Frank et al [44] studied the economic performance of a solar system, air-to-air heat pumps, and several solar- assisted heat pump systems for residential heating... where unglazed flat plate solar collectors acted as an evaporator for the R-13 4a They showed that the system is influenced significantly by collector area, speed of compressor, solar irradiation and storage volume Evaluation of a rice drying system using a solar assisted heat pump was carried out by Best et al [27] They developed a combined solar assisted- heat pump rice drying 11 Chapter 2 Literature... highest total saving produced on behalf of the solar system in comparison with the total expenditure of a conventional alternative during the life-cycle MacArthur [38] investigated a performance analysis and cost optimization of a solar- assisted heat pump system He demonstrated the performance of the system as a function of collector area Thermal storage volume was evaluated to determine the fraction of the... heat pump systems for space and process water heating Their procedure accounts for the variable efficiency and rate of energy delivery by the heat pump They reported that the capacity of the heat pump relative to the load requirement significantly affects the overall system performance Hawlader et al [26] performed analytical and experimental studies on a solar assisted heat pump water heating system, ... [11], and Prasertsan et al.[12] studied and analyzed a heat- pump dryer taking into account several important variables, such as ambient condition, ratio of recirculated air, the evaporator air by-pass ratio , the total mass flow rate along with the system characteristics, moisture extraction rate, and specific moisture extraction rate to analyze the heat pump system It was found that moisture extraction... performance and technical feasibility of the system for various applications, such as water heating, and space heating and cooling Morgan [19] investigated a direct expansion solar assisted heat pump using R-11 The heat pump was specially designed for use in a tropical climate, where the normal ambient temperature of the day above 250C permitted the operation of evaporator at a high temperature, 150C... graphical method for estimation the optimal collector area and evaluating the solar system economic effectiveness Tasdemiroglu and Awad [37] described a mathematical model for the optimization of solar collector area in a solar 14 Chapter 2 Literature Review heating system They presented an optimization procedure based on the estimation of the size of a solar system in terms of collector area that... chapter 1 2 Previous works on developments of solar assisted heat pump drying systems have been thoroughly reviewed A literature review on the solar assisted heat pump drying system is presented in chapter 2 3 Two evaporators, fitted in parallel mode, are used in the heat pump circuit, one acting as a dehumidifier and the other as a solar collector In addition an air collector absorbs solar energy and... long drying time due to low temperature drying The technical feasibility of solar drying has been demonstrated by a number of investigators It is possible to provide moderately heated air at a low enough investment using a solar air heater with simple design Additional advantages of solar drying are, free, nonpolluting, renewable, abundant energy source of the sun The main drawback of the solar system. .. the solar input His result demonstrates the feasibility of utilizing the system to heat water up to 900C with a COP varying from 2.5 to 3.5 Krakow et al [20] investigated a direct expansion solar assisted heat pump system using collector plates fitted with fins for space heating They asserted that solar source heat pump systems with glazed solar collector are preferable to systems with unglazed solar ... compressor, solar irradiation and storage volume Evaluation of a rice drying system using a solar assisted heat pump was carried out by Best et al [27] They developed a combined solar assisted- heat pump. .. et al [44] studied the economic performance of a solar system, air-to-air heat pumps, and several solar- assisted heat pump systems for residential heating They concluded that the air-to-air heat. .. such as water heating, and space heating and cooling Morgan [19] investigated a direct expansion solar assisted heat pump using R-11 The heat pump was specially designed for use in a tropical climate,