A SOLAR ASSISTED HEAT PUMP SYSTEM FOR DESALINATION

A SOLAR ASSISTED HEAT PUMP SYSTEM FOR DESALINATION ZAKARIA MOHD. AMIN NATIONAL UNIVERSITY OF SINGAPORE 2010 A SOLAR ASSISTED HEAT PUMP SYSTEM FOR DESALINATION ZAKARIA MOHD. AMIN (B.Sc.(Hons.),BUET) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF MECHANICAL ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2010 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION 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 wishes 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 extends his thanks to all the technical staffs in the thermal division, particularly Anwar Sadat , Roselina Abdullah ,Yeo Khee Ho, Hung-Ang Yan Leng, and Tan Tiong Thiam, 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, 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. Page i A SOLAR ASSISTED HEAT PUMP FOR DESALINATION TABLE OF CONTENTS ACKNOWLEDGEMENTS i TABLE OF CONTENTS .ii SUMMARY ix LIST OF FIGURE xii LIST OF TABLES . xviii NOMENCLATURE xix CHAPTER INTRODUCTION . 1.1 Background 1.2 Objectives . 1.3 Scope CHAPTER LITERATURE REVIEW . 2.1 Desalination 2.1.1 Desalination Process 2.1.2 Thermal desalting processes 2.1.4 Multi-effect distillation (MED) 11 2.1.5 Reverse Osmosis (RO) . 13 2.1.6 Vapor Compression (VC) . 14 2.1.7 Solar stills . 15 2.1.8 Other desalination processes 16 Page ii A SOLAR ASSISTED HEAT PUMP FOR DESALINATION 2.1.9 Comparisons of Different Desalination Processes . 17 2.1.10 Cost of Desalination Process . 19 2.1.11 Renewable Energy for Desalination Process . 21 2.2 Solar Assisted Heat Pump(SAHP) Systems . 22 2.2.1 SAHP for water heating . 24 2.2.2 SAHP for drying 25 2.2.3 SAHP for desalination . 26 2.3 Refrigerant 28 2.4 Solar Evaporator Collector (SEC) 29 2.5 Waste Heat 32 2.6 Photovoltaic System . 33 2.6.1 Photovoltaic cell structure 33 2.6.2 Types of photovoltaic solar cell . 35 2.6.3 Mono crystalline photovoltaic cell . 35 2.6.4 Amorphous silicon photovoltaic cell . 36 2.6.5 Poly crystalline photovoltaic cell . 36 CHAPTER EXPERIMENTS . 39 3.0 Description of the System 39 3.1 Solar Assisted Heat Pump (SAHP) system 41 3.1.2 Refrigerant flow of integrated SAHP 43 Page iii A SOLAR ASSISTED HEAT PUMP FOR DESALINATION 3.1.3 Working principle of desalination 45 3.1.4 Working principle of dryer . 47 3.1.5 Components of the SAHP System . 47 3.1.6 Compressor 48 3.1.7 Condenser 49 3.1.8Desalination Chamber . 49 3.1.9Water Cooled Condenser 51 3.1.10 Air Cooled Condenser 52 3.1.11 Thermostatic Expansion Valve 53 3.1.12 Evaporator 53 3.1.13 Desalination Cooling Unit . 54 3.1.14 Indoor Room Evaporator . 54 3.1.15 Solar Evaporator Collector (SEC) . 55 3.1.16 Solar Liquid collector 56 3.1.17 Electrical heater . 56 3.1.18 Refrigerant . 56 3.2 Photovoltaic 57 3.2.1 Mono Crystalline Cell 59 3.2.2 Poly Crystalline Cell 60 3.2.3 Tandem Cell . 60 Page iv A SOLAR ASSISTED HEAT PUMP FOR DESALINATION 3.3 Instrumentation and Control 60 3.3.1 Data Acquisition System . 62 3.3.2 Temperature Measurement . 62 3.3.3 Pressure Measurement 63 3.3.4 Flow Rate Measurement 63 3.3.5 Solar Radiation Measurement 64 3.3.6 Humidity Measurement . 64 3.3.7 Wind Speed Measurement . 64 3.3.8 Grid-tie-Inverter . 65 3.4 Test Procedure 65 3.4.1 Test Procedure for Heat-pump system 66 3.4.2 CHAPTER Test Procedure for Photovoltaic system . 67 MODELLING AND SIMULATION 69 4.1 Meteorological Condition of Singapore . 69 4.1.1 Meteorological model 72 4.2 Modeling of Heat Pump 72 4.2.1Compressor . 73 4.2.2Water condenser 74 4.2.3 Desalination chamber . 77 4.2.3.1 Thermodynamic flashing 78 Page v A SOLAR ASSISTED HEAT PUMP FOR DESALINATION 4.2.3.2 Condensing coil 78 4.2.3.3 Desalination cooling coil 80 4.2.4 Air condenser and drying chamber 81 4.2.5 Room Evaporator . 83 4.2.6 Solar Evaporator Collector (SEC) . 84 4.2.7 Thermostatic Expansion Valve 98 4.2.8 Pressure drop of refrigerant . 98 4.2.9 Liquid solar collector . 107 4.2.10 Coefficient of Performance 111 4.2.11 Performance Ratio . 111 4.3 Economic Analysis . 112 4.4 Simulation Algorithm . 114 4.5 Error Analysis . 118 CHAPTER RESULTS AND DISCUSSION 126 5.1 System Performance . 126 5.1.1 Meteorological condition of Singapore . 126 5.1.2 Desalination . 128 5.1.3 Water heating . 138 5.1.4 Drying 140 5.1.5 Air-conditioning . 141 Page vi A SOLAR ASSISTED HEAT PUMP FOR DESALINATION 5.1.6 Solar Evaporator Collector (SEC) . 143 5.1.7 Renewable Energy Absorption 147 5.2 Comparison of Experimental and Simulation Results . 153 5.2.1 Desalination . 153 5.2.2 Water heating . 154 5.2.3 Drying 155 5.2.4 Air-conditioning . 156 5.2.5 Evaporator-collector . 158 5.3 Paramedic Analysis of Heat Pump System 161 5.3.1 Heat transfer coefficient and pressure drop of SEC . 162 5.3.2 Effect of refrigerant flow rate on SEC Performance . 167 5.3.3 Effect of solar radiation on SEC performance . 170 5.3.4 Effect of ambient temperature on SEC performance . 174 5.3.5 Effect of relative humidity (RH) on SEC performance . 178 5.4 Parametric Study of Desalination . 182 5.5 Economic Analysis . 187 5.6 Comparison with Other Literature . 194 5.7 Photovoltaic System . 197 5.7.1 Effect of metrological condition 197 5.7.2 Photovoltaic power generation 199 Page vii A SOLAR ASSISTED HEAT PUMP FOR DESALINATION 5.7.3 Photovoltaic panel temperature 201 5.7.4 Photovoltaic Efficiency 202 5.7.5 Photovoltaic Power to Run the Blower 203 5.7.6 Solar Fraction (SF) . 205 5.7.7 Analyze Figure of Daily Gains in 30 random days 206 5.8 Design tool . 207 CHAPTER CONCLUSIONS 212 REFERENCES 215 APPENDIX A 230 APPENDIX B 234 APPENDIX C 235 APPENDIX D 237 APPENDIX E 241 APPENDIX F 251 APPENDIX G 257 APPENDIX H 261 APPENDIX I . 266 APPENDIX J . 269 Page viii A SOLAR ASSISTED HEAT PUMP FOR DESALINATION Pressure (bar) Pressure_ac_room vs Time 4.5 3.5 2.5 1.5 0.5 P_in P_out 10 15 20 25 30 35 40 45 50 55 60 65 70 75 Time(min) Figure.F.11. Refrigerant Pressure of Room evaporator Vs Time: Page 256 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION APPENDIX G Numerical solution of PDE using Crank-Nicholson method The governing equations of the energy balance on the evaporator collector subject to an initial condition and four boundary conditions are given in the previous chapter. This is to be solved numerically using Crank-Nicholson method. 1. Finite difference approximation for PDE for the interior area of collector. The partial differential equation for the interior area of collector is expressed as qu  2T  2T  c p T    k x y k t t t j 1 j 1 j j t x m 1 m m 1 x [1] Tm,n 1 Tm 1,n x ty n 1 Tm 1,n Tm , n y Tm,n 1 n n 1 y Figure G.1 Graphical form of Crank Nicholson method Crank-Nicholson method is to consider partial differential equation (PDE) as being satisfied at the midpoint of j and j+1 as shown in Figure G.1. Using Crank-Nicholson method, the following terms are expressed as: Page 257 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION j j 1   Tmj1, n  Tmj1, n  2Tmj, n Tmj1,1 n  Tmj1,1 n  2Tmj,n1   2T   2T  2T          x 2  x x x x    j j j j 1 j 1 j 1  2T  Tm, n 1  Tm, n 1  2Tm, n Tm, n 1  Tm, n 1  2Tm, n      y 2  y y  j 1 T  T  T j  T T j 1  T j  t t Substituting these terms into equation [1], gives U L j 1 r j 1 Tm, n  Tm 1, n  Tmj1,1 n  Tmj,n11  Tmj,n11  4Tmj,n1   pTmj,n1 2 1  r  S  U L  Tmj, n  Ta   Tmj1, n  Tmj1, n  Tmj, n 1  Tmj, n 1  4Tmj, n   pTmj, n 2  Where, we define: r  [2] k k  c  , and p  x y t Rearrangement of this equation gives U p  j 1  Tmj,n11  Tmj1,1 n  Tmj1,1 n  Tmj,n11   4  L   Tm, n r r   U 2p  j    Tmj, n 1  Tmj1, n  Tmj1, n  Tmj, n 1     L   Tm, n   S  U LTa  r r  r  [3] Equation [3] is the finite difference approximation of the governing equation [1] 2. Finite difference approximation for boundary conditions The partial differential equation for the boundary at y  and  x  W  D  is expressed as: qu  2T 2 T  c p T   U L T  Ta    k x k y y y k t [4] Using Crank-Nicholson method, the following terms are expressed as: Page 258 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION j j j j 1 j 1 j 1  2T  Tm 1,n  Tm 1,n  2Tm ,n Tm 1,n  Tm 1,n  2Tm ,n      x 2  x x  T  T j 1  T j  j j T Tm,n 1  Tm ,n  y y T T j 1  T j  t t Substituting these terms into equation [4], gives  U  2  p  j 1 Tmj1,1 n  Tmj1,1 n   2  L 1   Tm, n  r  y  r    U  2  p  j   Tmj1, n  Tmj1, n  2Tmj, n 1     L 1   Tm, n   S  U LTa   r  y  r  r  Similarly, at y  L and  x  [5] W  D  T Tm,n  Tm,n 1   y y The partial differential equation [1] can be written as:  U  2  p  j 1 Tmj1,1 n  Tmj1,1 n   2  L 1   Tm,n  r  y r      U  2  p  j   Tmj1,n  Tmj1,n  2Tmj,n 1     L 1   Tm,n   S  U LTa   r  y  r  r  [6] At x  and  y  L , partial differential equation is expressed as: qu  2T T  c p T    k y x x k t [7] Use Crank-Nicholson method to write it in finite difference approximation form: U p  j 1  Tmj,n11  Tmj,n11  2Tmj1,1 n   4  L   Tm ,n r r   2p  j  U   Tmj,n 1  Tmj,n 1  2Tmj1,n     L   Tm ,n   S  U LTa  r r  r  [8] Page 259 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION At x (W  D) and  y  L , partial differential equation is expressed as: qu T   k D x T  T  f  1  k D    h  D C  b   fi i  [9]  c p T k t Using Crank-Nicholson method, the following terms are expressed as: T T x T t j 1 T T j   Tmj,n  Tmj1,n  x j 1 T T j  t Substituting these terms into equation[9], gives  p  U L    Tmj,n1   p  U L  4r  Where   x   j x      Tm,n  4r Tmj1,n   S  U LTa  T f  D D D D   1 h fi Di  Cb Page 260 [10] A SOLAR ASSISTED HEAT PUMP FOR DESALINATION APPENDIX H List of devices 1. Solar Evaporator-Collector Unit a. Area 2m2 (2 X ) b. Absorber plate 2mm thick copper plate(copper tube is bonded to the absorbing plate in a serpentine fashion) c. Surface treatment Black paint coating. Absorptivity: 90%, Emissivity: 90% d. Back insulation Made of fiberglass wool of thickness 50mm e. Collector tilt 10 degrees f. Portable frame Stainless steel material g. Thermocouple insert Total 1st collector 2nd collector 2. Evaporator (forced draft with two fans) a. Type Cross flow fin and tube b. Total air flow rate 9.9 m3/min c. Mounted story below 3. Compressor with inverter control a. Type Reciprocating Open type b. Cooling capacity 34 kW c. Motor output 7.5 kW Page 261 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION d. Bore 105 mm e. Stroke 75 mm f. Cylinder g. Motor speed 315 – 565 rpm 4. Water cooled condenser (water tank) a. Size 300 liters (dimensions: 0.6m x 0.6m x 0.83m) b. Condenser coil Spiral shape copper tube c. Insulation Made of FRP fiberglass of thickness 50mm d. Thermocouple insert One thermocouple in the middle to measure water temperature 5. Air cool condenser a. Type Air cooled fin (Aluminum) and tube (Copper) b. Face area 22.65m2 c. Tube diameter 3/8 inch 6. Drying Chamber a. Dimension 0.6m x 0.6m x 0.4m b. Material Stainless steel c. Insulation Internally insulated with Armaflex 7. Blower a. Type Axial flow fan b. Air flow rate 6200 m3/hour c. Motor speed 1440RPM(maximum) d. Static pressure 200Pa Page 262 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION e. Electric Power 0.75kW f. Starting Amp 6.5 g. Supply 415V / 3Φ / 50 Hz h. FLC 1.84 8. Expansion Valves (3 unit) a. Type Thermostatic expansion valve b. Capacity 6.7kW & 10.5kW 9. High/Low Pressure Cut-off (safety device) a. High pressure limits 10-20 bar b. Low pressure limits 0-5 bar 10. Frequency Inverter a. Capacity 11 kW b. Frequency range 0-50Hz, phase 11. Liquid solar collector a. Dimensions 1000x1980x80 mm b. Tube material copper c. Plate material aluminum d. Tube outer diameter / 12.7 mm / 0.7 mm thickness e. No. of headers f. No.of risers g. Tube spacing 130 mm h. Insulation material Insulwool Page 263 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION e. Portable frame Stainless steel material 13. Desalination Chamber(vacuum standard) a. Volume 25.5 liters b. Outer diameter 255 mm c. Height 500 mm d. Chamber material Stainless steel 316 with glass window e. Coil material copper f. Length of cooling coil 3.5 m g. Length of condenser 2m coil h. Tube outer diameter / 9.5 mm / mm thickness i. Portable frame Stainless steel material j. Insulation Internally insulated with Armaflex 14. Vacuum pump(for desalination chamber) 15. Saline Water Pre-heater (Max. Temperature : 80°C ) with controller 16. PV unit (1 kW) to run blower and pump a. PV cell of three types b. PV panel with a portable frame made of Stainless steel c. Battery Page 264 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION d. DC- to – AC convertor 18. Water pump (Stainless steel) to circulate saline water 19. Filter & Accumulator 20. Refrigerant R-134a 21. Copper piping with insulation 22. Bypass : a) Solar evaporator collector (Item 1) b) Room evaporator (Item 2) c) Water condenser(Item 4) d) Air cool condenser (Item 5) e) Desalination chamber cooling coil (Item 13) f) Desalination chamber heating coil (Item 13) Page 265 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION APPENDIX I I.1: Difference before and after data smoothing Performance ratio 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 y = 2x10-07x2 + 1x10-04x + 0.5227 R2 = 0.5254 0.10 0.00 200 400 600 800 1000 1200 Solar irradiation (W/sq m) PR Poly. (PR) Figure I.1: Before data smoothing, PR vs solar irradiation Performance ratio 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 y = 2x10-07x2 + 1x10-04x + 0.5178 R2 = 0.9464 0.10 0.00 200 400 600 800 1000 1200 Solar irradiation (W/sq m) PR smoothing Poly. (smoothing) Figure I.2 : After data smoothing, PR vs solar irradiation Page 266 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION I.2: Techniques for data smoothing [127] Data smoothing techniques attempt to forecast trends or patterns through the removal of “noise”. The basic assumption is that the underlying process producing the data is smooth. Below are some of the available smoothing methods. 1. Random This method is best when each period's data has no relationship to the pattern in the previous data. Under this condition, the best prediction for the next value in a series is simply the average of all previous data points. 2. Random Walk A random walk exists if the next data point is equal to the last data point plus some random deviation α. Instead of trying to directly predict the next data point, the change from one data to the other is predicted. +α 3. Moving Average This is one of the simplest but also most versatile and widely used of all techniques. One disadvantage is that it will lag slightly behind the real trend because it is influenced by prior as well as present data. The moving average follows a recursive formula: where:    N is the number of prior periods to include in the moving average Aj is the actual value at time j Fj is the forecasted value at time j n is a user-supplied constant greater than zero defining the number of consecutive points to average. Higher values cause greater smoothing. Double Moving Average is done by applying the Moving Average twice, which smoothes the already smoothed series. Page 267 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION 4. Simple Exponential Smoothing This method works well if the data contains no trend or cyclic pattern and the most recent data points are more significant than earlier points. a is the smoothing constant. 5. Linear Exponential Smoothing (Holt's method) This method works well if the data contains a trend but no cyclic pattern. a is the level smoothing constant and b is the trend smoothing constant, where 0[...]... insulation was first used in a heat pump system by Franklin et al.[7] Hawlader et al.[4] performed analytical and experimental studies on a solar Page 3 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION assisted heat pump using unglazed, flat plate solar collectors Chaturvedi et al.[8, 9] found a variation of the evaporator temperature from 0°C to 10°C above the ambient temperature under favorable solar conditions... desalination, water heating and drying with renewable heat sources: solar energy, ambient energy and waste heat by developing a solar- assisted assisted heat- pump system Additionally, in the condenser section water heating and drying are incorporated to analyze the performance of an integrated heat pump system Again for the integrated system, it Page 2 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION requires electricity... of all known energy sources The low temperature thermal requirement of a heat pump makes it an Page 1 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION excellent match for the use of solar energy The combination of solar energy and heat pump system can bring about various thermal applications for domestic and industrial use, such as water heating, desalination, solar drying, space cooling, space heating and... water heating and air heating and thus drying Hence, the solar assisted heat pump system can perform as a desalination unit, water heater, clothes dryer and air conditioner For the solarelectric energy, there are three main silicon-based photovoltaic solar cells, namely: mono crystalline, poly crystalline and tandem cells All three types have been installed along with solar assisted heat pump system. .. waste of energy, but also causes severe pollution, Global Warming Thus, a heat pump can be a great asset for thermal applications which utilizes solar, ambient and waste heat And matching the solar heat pump to desalination can resolve two major problems: energy crisis and water shortage In this study, an attempt has been made to recover the condenser heat and utilize it in desalination, water heating... innovative changes The integration of solar desalination and heat pump presents an impressive method of solar desalination From an energy point of view, the solar assisted heat pump provides a high overall efficiency as it makes use of both solar and ambient energy The objectives of this project include design, construction and performance evaluation of a solar assisted heat- pump system for desalination After... from air con and uses this energy for desalination, water heating and drying The renewable energy is harnessed by three different types of collectors, 1) Solar Evaporator Collector (SEC), which captures energy from solar radiation and ambient air, 2) Liquid Solar Collector for preheating water for Desalination, 3) Photovoltaic system for the conversion of solar irradiation Page ix A SOLAR ASSISTED HEAT. .. of desalination, in particular those closely associated with the use of desalination, solar assisted heat pump and solar collectors 2.1 Desalination Desalination is the process whereby potable water is recovered from a salt solution, such as seawater or brackish water The desalination process has been known since ancient times, but perhaps the earliest known seawater desalination process took place... al.[6] performed an investigation on the steady state thermal performance of a direct expansion solar- assisted heat pump and indicated that this system offers significant advantage in terms of superior thermal performance A conventional vapor compression air conditioning system collects the heat from a heat source (air-con room) and discharges it to the atmosphere This dissipated heat is not only a. .. operation of solar energy systems In this regard, an integrated solar heat pump desalination system is designed, built and analyzed at the Department of Mechanical Engineering, National University of Singapore, NUS In order to utilize maximum energy available from the system, it is integrated with water heater, dryer and room air-con system The system collects energy from solar, ambient and waste heat . A SOLAR ASSISTED HEAT PUMP SYSTEM FOR DESALINATION ZAKARIA MOHD. AMIN NATIONAL UNIVERSITY OF SINGAPORE 2010 A SOLAR ASSISTED HEAT PUMP SYSTEM FOR DESALINATION. pre- heating water for Desalination, 3) Photovoltaic system for the conversion of solar irradiation A SOLAR ASSISTED HEAT PUMP FOR DESALINATION Page x to electricity for running pump and blower J 269 A SOLAR ASSISTED HEAT PUMP FOR DESALINATION Page ix SUMMARY Solar desalination, although investigated for several decades and its potential is never doubted, has only recently