An experimental study is conducted to show the influence of the tubes material type of the heat exchanger on the refrigeration system performance. The system is operated by using R134a as a working fluid, 2 mm internal diameter, and different lengths of capillary tubes which were 120, 135, and 150 cm. The experimental results showed that when increasing the refrigerant mass flowrates led to reducing each of the performance coefficient COP, number of transfer unit NTU and evaporator effectiveness ε. However, the highest improvement had appeared for each parameter COP, NTU, and ε which were 21%, 113.38%, and 59.42% respectively at a capillary tube length of 120 cm and [Formula: see text] = 3.19 g/s compared to the length of capillary tube 150 cm. Besides, it was found an increase in [Formula: see text] with the incrementing in the capillary tube length from 120 cm to 150 cm. The biggest percentage of compression power was 23% at the capillary tube length of 150 cm compared to others at [Formula: see text] = 3.71 g/s. Finally, the experimental results of COP and [Formula: see text] were validated by comparing them with other publications.
An experimental study was conducted to demonstrate the effect of a capillary tube length on the refrigeration system performance by adding heat exchanger. The heat exchanger was designed by laterally welding 70cm of capillary tube with the suction line. Different lengths of the capillary tubes, i.e. 160, 175, and 190cm, were studied; besides different refrigerant flow rates and condenser air fan velocities for both cases of adiabatic and nonadiabatic capillary tube. The experimental results showed an increase in the system performance by 17.96% with a decrease in the nonadiabatic capillary tube length from 190 to 160 cm at mass flow rate of 17.3 kg/hr and air velocity of 3 m/s. In addition, the increase in the air-speed has led to a COP increment by 17.47% at mass flow rate of 18.9 kg/hr and capillary tube length of 190 cm. Finally, at the capillary tube length of 190cm and refrigerant mass flow rate of 2.4g/s, the maximum enhancement of the refrigeration system performance and exergy efficiency by 6.7% and 35%, respectively, was achieved for air speed of 1m/s and 3 m/s , compared to the reference case of the adiabatic capillary tubes.
An experimental compression refrigeration system performance study was presented in this research depending on the change of the capillary tube length and by using (R134a). The tests were done for three capillary tube lengths (80,100,120cm) and changing mass flow rate for each length. Their values were (2 6g/s) with capillary tube diameter (2mm). The results showed that the (COP) decreases by (38.14%) as the mass flow rate increases from (2 6g/s), and by (6.65%) as the capillary tube length increases from (80- 120 cm). At (L=80Cm) the (COP) value will be greater than it’s value at (L=120Cm) for lowest mass flow rate, while it’s values converge for all lengths at high mass flow rate .Also it was declared that (COP) will decrease as the condenser temperature increases for all lengths. The study showed that the compressor compression power increases as the condenser temperature increases by (68.36%), and increases as the capillary tube length increases by (9.54%) with convergence value at (100 cm) and (120 cm) . This study showed also that sub-cooling temperature stays constant at low flow rates, and decreases at higher flow rates by (34.35%). Through this study was found best length used in refrigeration cycle at lowest mass flow rate (2.78 g/s) is (80Cm) which will give highest performance and lowest compression power, and at high mass flow rate (5.83 g/s) found the length (100Cm) will give highest performance and lowest compression power.
In this research an experimental study was carried out to show the effect of time ofopening and closing the solenoid valve on the effectiveness of finned cross flow heatexchanger, which has changed the time of opening and closing the solenoid valve (2, 4,6 sec.) with change the mass flow rate of water each time and the range values between(0.027-0.0816 kg/s) with constant of mass flow rate of air at (0.032 kg/s).The results obtained from experiment works that the decreasing in the time of openingand closing the solenoid valve from (6 sec.) to (2 sec.) leads to increase internal heattransfer coefficient (hi) the highest increase was by (18.37%) at mass flow rate of water(0.027 kg/s) and increase the overall heat transfer coefficient (U) and the highestpercentage of increase (7.36%) at mass flow rate of water (0.027 kg/s).The experimental results obtained show that the increasing both the number of unitstransmitted (NTU) and effectiveness of the finned heat exchanger when decrease thetime of opening and closing the solenoid valve from (6 sec.) to (2 sec.) and the highestpercentage of the increase occurring is (8.4%) and (1.74%) respectively at mass flowrate of water (0.027 kg/s).
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