The performance of vapor compression refrigeration system with controllable speed compressor and vapor and liquid refrigerant injection techniques is experimentally investigated. For this purpose, a 5-tons (17.6 kW) split air conditioner unit charged with R-22 refrigerant was modified and equipped with, frequency inverter, secondary capillary tube, and liquid pressure amplification pump (LPA). Vapor refrigerant was injected into the accumulator with three injection mass ratios 2, 3, and 4%. LPA pump was used to inject liquid refrigerant from the condenser outlet to the discharge line with injection mass ratios 0.5%, 1.5%, and 2%. The compressor speed was controlled by frequency inverter, where the range of the frequency used was from 35 to 60 Hz with 5 Hz step. The results showed that the coefficient of performance (COP) of the modified system using vapor injection technique was improved by 11.26% compared to the conventional system, and the suction temperature reduced from 10.3 to -0.1°C with 3% vapor injection ratio. The best enhancement in COP was 9.9% for the 0.5% liquid injection ratio. Reduction of the compressor speed leads to improve the COP by 18% and reduces the compressor power by 36.4% at frequency 35Hz. Using the vapor injection with variable speed compressor improved the COP of the modified system by 75% at 35 Hz and 2% injection mass ratio.
An experimental investigation of refrigerant R-134a two-phase flow condensation heat transfer coefficient and pressure drop in condenser tube section of refrigeration system under different operating conditions is presented. The experimental and theoretical investigations are based on test conditions in range of 10 -17 kW/m 2 for heat flux, 42-63 kg/m 2 s for mass flux, vapor quality 1-0.03 and saturation temperature 44 to 49˚C. The experimental tests are conducted on test rig supplied with a test section to simulate the water cooled double pipe heat exchanger, which is designed and constructed in the present work. "The experimental results have revealed that, the heat flux and mass flux have significant impacts on the heat transfer coefficient. "The heat transfer coefficient was increased with increase in heat flux and mass flux at prescribed test conditions, where the enhancement in heat transfer coefficient was about 47% and 14% for relatively higher heat flux and mass flux, respectively. "The enhancement in the heat transfer coefficient was about 51% for relatively lower saturation temperature 45.97˚C and 43% for higher vapor quality 0.88 compared to other values at constant test conditions. "The pressure drop was higher in the range of 12% and 49% for relatively higher mass flux and heat flux respectively. "The present work results have validated by comparison with predictive models and with similar research work results and the comparison has revealed an acceptable agreement.
The impact of the solar photovoltaic cell temperature on module output performance parameters is investigated experimentally under conditions of Baghdad city climate in the present study. The tests are conducted using a test rig for Polycrystalline silicon solar panel with rated capacity 300W and equipped with measuring devices. Test conditions are based on three months duration, June, July and August of year 2019 through the period from 8AM to 4PM per day. This period represents the highest ambient temperatures through summer months in Baghdad city in Iraq. The results have shown that, under the test conditions for cell temperature with range 45-65°C a significant reduction in the output power, efficiency and fill factor with module temperature rise were observed. The loss in the open circuit voltage and output power of the photovoltaic module was about-0.104/°C and-1.3/°C respectively. The reductions in the current and voltage at maximum output power with temperature increasing were about-5.24% and-5.45% respectively. The drops in the efficiency and fill factor of the photovoltaic module due to the module temperature increase were 9.62% and 12.96% respectively compared to that at standard conditions. The temperature coefficient of the maximum power was-0.52% for the solar photovoltaic module under test conditions.
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