7/10/20 AAR WEB Series-III 9 th , July., 2020 1. The temperature ranges of Ammonia Ultra low temperature freezing plant vapor compression refrigeration systems using Ammonia 2. Applications 3. Ammonia low temperature refrigeration systems 4. Case Study Hiroyuki Egashira Mayekawa Mfg. Co., Ltd. AAR WEBINAR SERIES -3 9 July 2020 1 AAR WEBINAR SERIES -3 9 July 2020 2 1 2 What is temperature? 1. Temperature is a kinetic energy of molecules that make a substance. • Energy level is low, the molecules stick together, and form Solid. 1. The temperature ranges of vapor compression refrigeration systems AAR WEBINAR SERIES -3 9 July 2020 3 AAR WEBINAR SERIES -3 9 July 2020 4 3 4 What is temperature? What is temperature? • This process requires the • When the energy level increase and the absorption of energy by the bonding of the molecules loosen, solid molecule, and the level of energy melts and becomes liquid. in the molecule is measured as • When the energy level goes higher, and temperature of the substance. the molecule starts to move freely, the • State of no energy at all in the substance become gas/vapor substance is absolute 0 temperature, or 0K(Kelvin). In terms of Celsius,- 273.15deg.C. AAR WEBINAR SERIES -3 9 July 2020 5 AAR WEBINAR SERIES -3 9 July 2020 6 5 6 1
7/10/20 Change of Phase P-H Diagram and Phase Substances change its phases: • Solid • Liquid • Vapor Each substance has specific temperature , pressure and specific energy level to change phases This can be visualized in P-H Diagram Example of phases (CO2) AAR WEBINAR SERIES -3 9 July 2020 7 AAR WEBINAR SERIES -3 9 July 2020 8 7 8 Phase of the material Vapor compression refrigeration Cycle Previous slide is CO2 P-H diagram, that • Vapor compression refrigeration shows the 3 phases of CO2. system operate between vapor and I could not find Ammonia P-H diagram to liquid. show the same phase changes, but in the Heat same manner, vapor, liquid and solid Rejection states exist for Ammonia. 2 3 Condenser Expansion Compressor Valve Evaporator 4 1 Heat Absorption AAR WEBINAR SERIES -3 9 July 2020 9 AAR WEBINAR SERIES -3 9 July 2020 10 9 10 Vapor Compression Refrigeration Cycle on Vapor compression refrigeration Cycle P-H Diagram As shown in the previous slide, the vapor compression refrigeration cycle operate where the liquid and gas co-exist. Example of phases (CO2) AAR WEBINAR SERIES -3 9 July 2020 11 AAR WEBINAR SERIES -3 9 July 2020 12 11 12 2
7/10/20 Vapor compression refrigeration Cycle Vapor compression refrigeration Cycle We usually operate at the very high pressure side of Ammonia, so we do not think about the solid state of Ammonia. 112.3kg/hr However, Ammonia also reaches solid state at -77.72 deg.C., at around 0.06bar A. 100kg/hr+12.3kg/hr 35.5kW P-H Diagram NH3 AAR WEBINAR SERIES -3 9 July 2020 13 AAR WEBINAR SERIES -3 9 July 2020 14 13 14 Vapor compression refrigeration system Vapor compression refrigeration system Evaporating temperature limits Evaporating temperature limits Of various substance Of various substance I selected Mol Weight Te at 0barG Te at -0.8barG Freezing Point 1. the atmospheric pressure as a bench Ammonia NH3 17 -33.6 -61.6 -77.73 mark. Carbon Dioxide CO2 44 - - -56.6 2. -0.8barG, as economical limit Propane C3H8 44 -42.4 -73.6 -187.7 3. freezing point as the limit set by the law Nitrogen N2 28 -196.0 -206.3 -210 of physics. . AAR WEBINAR SERIES -3 9 July 2020 15 AAR WEBINAR SERIES -3 9 July 2020 16 15 16 Vapor compression refrigeration system Vapor compression refrigeration system Evaporating temperature limits Evaporating temperature limits Of various substance Of various substance Please note: CO2 has a peculiar characteristics. 1. -0.8 barG pressure, I consider as the CO2 freezes at -56.6deg.C., at 5.2bar.A. operational limit of standard rotating The temperature limit of CO2 vapor equipment. compression system is much higher than 2. Freezing point is where vapor Ammonia. compression system cannot work Considering CO2’s efficiency does not because there is no liquid. match Ammonia below -40deg.C., the application of CO2 is limited between -40 and -50deg.C only. AAR WEBINAR SERIES -3 9 July 2020 17 AAR WEBINAR SERIES -3 9 July 2020 18 17 18 3
7/10/20 Vapor compression refrigeration system Vapor compression refrigeration system Comparison of NH3 and CO2 (Booster) NH3 CO2 Propane’s evaporating temperature is -73.6 Tc deg.C -5 -5 deg.C. at -0.8barG. So as it can achieve Te deg.C -50 -50 approx. 10 deg.C. lower than Ammonia. Swept Volume m3/hr 659 659 In this case, the problem is, Propane is Pd kg/cm2 3.62 31.1 highly explosive substance. Ps kg/cm2 0.42 6.96 Weight flow kg/hr 186.1 9409 Capacity kW 64.0 638.8 BkW 30.2 272.4 COP 2.12 2.35 AAR WEBINAR SERIES -3 9 July 2020 19 AAR WEBINAR SERIES -3 9 July 2020 20 19 20 Vapor compression refrigeration system Vapor compression refrigeration system Comparison of NH3 and CO2 (Booster) Comparison of NH3 and CO2 (Booster) As you can see, for the temperature of Saving of 10% of booster power is -50deg.C evaporation and -5 deg.C. negligible for the entire system. condensing, CO2 have 10 times the Also consider the high pressure design for capacity at 9 times the power. the discharge side of CO2 and the limited This shows that it requires 1/10 the application range of -45 to -55. size of compressor for CO2 cascade system, but in terms of power saving, Down to -60deg.C. can be achieved by 10% of the booster. Ammonia, there is no reason for us to In the tropical climate, high stage has invest for CO2 cascade system. to be Ammonia. AAR WEBINAR SERIES -3 9 July 2020 21 AAR WEBINAR SERIES -3 9 July 2020 22 21 22 Vapor compression refrigeration system Vapor compression refrigeration system Comparison of NH3 and Propane (Booster) Comparison of Propane and CO2 (Booster) NH3 PROPANE For the low temperature application with Tc -5 -5 cascade system, Propane is a better Te -60 -60 option. Swept Volume(m3/hr) 1210 1210 However, Propane is an explosive gas and Pd kg/cm2 3.62 4.11 system as well as the handling of the gas Ps kg/cm2 0.22 0.44 would cost dearly. Weight flow kg/hr 222.5 1157 Capacity(kW) 75.3 104.4 BkW 57.1 69.2 COP 1.32 1.51 AAR WEBINAR SERIES -3 9 July 2020 23 AAR WEBINAR SERIES -3 9 July 2020 24 23 24 4
7/10/20 Ammonia low temperature application Down to -60deg.C. Ammonia is the best refrigerant, since we can achieve the temperature with the equipment we already have. 1. Applications What are the specific application for this kind of temperature? AAR WEBINAR SERIES -3 9 July 2020 25 AAR WEBINAR SERIES -3 9 July 2020 26 25 26 1. Food Preservation 1. Food Preservation Most of the products can be stored for Great exceptions are: months at -25 deg.C. • Premium Grade Ice Cream -30deg.C. • Premium Grade Tuna -60deg.C. AAR WEBINAR SERIES -3 9 July 2020 27 AAR WEBINAR SERIES -3 9 July 2020 28 27 28 Freezing of Food Freezing of Food For the food freezing, the faster the better. Low temperature is essential for the fast freezing. Before Freezing Normal Freezing Quick Freezing However, the low temperature alone does not insure the fast freezing. Faster the freezing, ice crystal formed in the cell is smaller, and less damages to the cell membrane. With damaged cell membrane, cytoplasm flows out at the time of defrost. AAR WEBINAR SERIES -3 9 July 2020 29 AAR WEBINAR SERIES -3 9 July 2020 30 29 30 5
7/10/20 Freezing of Food Freezing of Food Typical temperature pattern of freezing. Only after the freezing, the temperature goes Initial temperature is high. down. The refrigeration system designed for low It quickly goes near freezing point, then stay temperature operate at higher temperature most there. of the time. AAR WEBINAR SERIES -3 9 July 2020 31 AAR WEBINAR SERIES -3 9 July 2020 32 31 32 Freezing of Food Freezing of Food Since the lower the temperature, the cost of freezing is higher, it is always the balance between the cost of freezing and cost of storage against market price. Typical temperature pattern of freezing. Surface freezes immediately ,but it will take longer for the center to freeze. AAR WEBINAR SERIES -3 9 July 2020 33 AAR WEBINAR SERIES -3 9 July 2020 34 33 34 Freezing of Food Freezing of Food IQF is a solution that make a consistent low Impingement freezer improve the heat transfer temperature operation and quick freezing of surface to shorten the freezing time. possible Conventional Air Flow Impingement Air Flow Uniform Flow One Side Two Sice Im pinging Jet Cold Air Cold Air Cold Air Slit Coanda Effect Slit Slit Im pinging Jet Coanda Effect Product Cold Air AAR WEBINAR SERIES -3 9 July 2020 35 AAR WEBINAR SERIES -3 9 July 2020 36 35 36 6
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