A 5 ton heat pump system with R22 was improved by Liquid Pressure Amplification (LPA) and refrigerant injection technologies. Three approaches for refrigerant injection were used. The first one was by mixture injection in suction line through accumulator; the second one was by liquid refrigerant injection through discharge line, while the third was a hybrid injection, in which vapour and liquid refrigerant were injected both simultaneously. For both approaches two and three LPA technique was used. The range of volume ratio of injected mixture and liquid was 1 to 7%, and 1 to 10% respectively, and in the hybrid injection, the volume ratio of injected mixture was 1 to 3% and for injected liquid was as mentioned above. The following improvement in cycle performance factors were achieved, for mixture injection 5.33%, for liquid injection 29.4%, and 33.45% for hybrid injection. The effect of condensing pressure on the cycle performance was studied also in this work. Keyword: Refrigeration, Refrigerant injection, LPA technology, Heat pump INTRODUCTION or a number of years LPA technology is available in the market for Vapour Compression Refrigeration (VCR) systems with direct expansion evaporator, but has not as yet found wide-range applications [1]. LPA achieving energy efficiency in the VCR systems by reducing compressor discharge pressure, as well as, compression ratio [2]. In LPA systems, liquid refrigerant entering the liquid line is pressurized by centrifugal pump. The amount of pressurization is greater than the pressure drop through condenser. This permits the pressure of the condenser to be varied in line with variations of ambient temperature, leading to reduce the discharge pressures, during low ambient temperatures periods. Working at low condensing pressure reduces compressor power consumption and increases refrigeration capacity [1]. By increasing the pressure of liquid refrigerant, the associated saturation temperature is raised, while the actual temperature of the liquid constant. Therefore liquid becomes sub-cooled and will not flash if exposed to pressure drop in the liquid line. De-superheating can be achieved by injection liquid refrigerant, from the same pump, into the discharge line; in such a way without affecting the refrigerant mass flow rate through the evaporation process. The injected liquid flashes into superheated vapour leading to reduce the discharge temperature closer to condensing temperature. As a result, less surface area in the condenser is required for de-superheating of vapour and more degree of sub-cooling. Fig. 1 shows LPA technology for VCR cycles [2]. Points (1-2-3-4) represent conventional VCR cycle and (a-b-c-d-e) represent VCR cycle with LPA technology. F Eng. &Tech.Journal, Vol.34,Part (A), No.14,2016 Theoretical Study of Refrigerant Injection Technology Effect on Heat Pump Cycle Performance

Theoretical Study of Refrigerant Injection Technology Effect on Heat Pump Cycle Performance

Refrigerant injection techniques are considered as modifications to vapor compression refrigeration systems to improve the performance of these systems when operating at high or low ambient temperatures. In this study a liquid and vapor refrigerant injections were implemented using heat exchangers arrangement. An investigation to the effects of these techniques on the performance of refrigeration cycle was conducted. A decrease in discharge temperature was obtained using hybrid injection cycles from 20% to 19% when the ambient temperature varies from 14°C to 8°C. Also the decrease in pressure ratio varied from 24% at an ambient temperature of 14°C to 18% at 8°C. The enhancement in performance factor varied from 35% at 14 °C to 28% at 8 °C.

/pdf/effect-of-different-refrigerant-injection-techniques-on-heat-2217sxuzji.pdf

Effect of Different Refrigerant Injection Techniques on Heat Pumpcycle Performance

An adsorption heat pipe was designed and built from a stainless steel tube of 32 mm outer diameter, 30 mm inner diameter and 1000 mm long, the inner surface of the tube was coated by 10 mm thickness of active carbon, which was assumed to be the adsorbent, while the adsorbent was assumed to be the methanol, or acetone. The adsorption heat pipe consist of three zones, namely adsorption/ desorption, adiabatic and evaporation/condensation zones. Electrical heater with variables capacity is used to heat up the unit generator during desorption process, water was used to cool the condenser, while air was used to cool the generator. Two types of adsorption pair are used, namely active carbon-methanol and active carbon-acetone. The effect of heat input to the generator on the heat pipe surface temperature and evaporator temperature are studied. The results showed that the adsorption heat pipe can work at a relatively low temperature namely 70-100 o C, the time required for cooling process in the range of 18 to 24 minutes, and activated carbon – Acetone pair gave a good behavior for the heat pipe due to the short cycle– time compared with that for activated carbon – Methanol

/pdf/investigation-of-the-performance-of-a-solar-powered-4626zp3omm.pdf

Investigation of the Performance of a Solar Powered Adsorption Heat Pipe

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Effect of Different Refrigerant Injection Techniques on Heat Pumpcycle Performance

Investigation of the Performance of a Solar Powered Adsorption Heat Pipe