2023-2 Mechanical Engineering Research Title: Refrigeration Cycle Experiment Submission date: Department: Student ID: Professor: Teaching Assistants: 1. Introduction and Theory Thermodynamics Laws Zeroth Law of Thermodynamics (Thermal Equilibrium) If two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. This law defines the concept of temperature. First Law of Thermodynamics (Law of Energy Conservation) Energy cannot be created or destroyed; it can only be transformed from one form to another. The total energy of a system remains constant, though its form may change. Second Law of Thermodynamics (Entropy Increase Law) Entropy, or the degree of disorder, always increases or at least remains constant in an isolated system. This implies that heat naturally flows from a higher temperature to a lower temperature. Third Law of Thermodynamics As the temperature approaches absolute zero (0K, -273.15°C), the entropy of a pure cryshe high-temperature, high-pressure refrigerant gas, which has passed through the compressor, to move through its coils. During this process, the refrigerant releases heat to the surrounding medium (air or water). As the heat is discharged, the refrigerant gas changes into a saturated liquid state. This is a crucial step in removing heat from the cycle, enabling the refrigerant to move to the next stage, the expansion valve. Expansion Valve The expansion valve is used to reduce the pressure of the refrigerant. After passing through the condenser, the refrigerant in a high-pressure saturated liquid state passes through the expansion valve, where its pressure drops significantly. As the pressure decreases, the refrigerant rapidly expands and its temperature lowers. This reduction in temperature prepares the refrigerant for its next phase in the evaporator, allowing it to efficiently absorb heat before moving there. Evaporator In the evaporator, the low-pressure refrigerant passes through board. Measure and record the pressure at both the inlet and outlet of the compressor, as displayed on the pressure gauge. Utilize the CoolPack program to draw a P-h (Pressure-enthalpy) diagram. Analyze this diagram to assess the performance of the refrigeration cycle. 3. Experimental results Position Temperature (℃) Compressor. In 38.3 Compressor. Out 85.2 Expansion Valve 1. In 32.3 Expansion Valve 2. In 28.9 Heat Exchanger 1. In -27.3 Heat Exchanger 1. Out 18.8 Heat Exchanger 2. In 65.1 Heat Exchanger 2. Out 33.3 Heat Exchanger 1. Temp 29.2 Heat Exchanger 2. Temp 15.1 Outside 25.8 Ideal point 1 2 3 4 5 6 Temperature (℃) -4.824 82.113 82.113 53.692 N/A -4.824 Pressure (Bar) 1.1 14.8 14.8 14.8 1.1 1.1 Enthalpy (kj/kg) 398.646 458.247 458.247 277.220 277.220 398.646 Real point 1 2 3 4 5 6 Temperature (℃) -7.299 125.285 117.264 29.999 N/A -4.824 Pressure (Bar) 0.422 23.527 14.800 7.924 1.240 1.100 Enthalpy (kj/kg) 398.646 498.640 498.640 241.461 241.461 398.646 Cool Pack Input Values Evautlet is the same as the pressure at the compressor inlet (1.1 bar). 1.1bar- 0.961bar = 0.139bar DP Condenser It's the pressure difference (or temperature difference) from the inlet of the condenser to the inlet of the expansion valve. However, as the expansion valve is in the compressed water range, it cannot be calculated using the temperature difference. Therefore, find the pressure at 31 degrees on the ph diagram (7.924 bar). Additionally, the pressure at the inlet of the condenser is the same as the pressure at the outlet of the compressor (14.8 bar). 14.8bar – 7.924bar = 6.876bar DP suction line It's the pressure difference (or temperature difference) from the outlet of the evaporator to the inlet of the compressor. 38.3-18.8=19.5K DP Liquid line It's the pressure difference (or temperature difference) after adiabatic expansion at the inlet point of the expansion valve (0). DP Discharge line It's the pressure difference (or temperature difference) from the outlet of the compressorepancy is due to the numerous DP values in each component. Reasons for these DPs include energy loss due to internal friction and heat exchange such as heat conduction. Improving these aspects to reduce the DP values can bring the cycle closer to the ideal one, and even though the compressor efficiency in the experiment was 0.596, it could potentially reach 1. Other potential sources of error in the experiment include the experimental environment. The experiment was conducted indoors, but in actual air conditioning systems used in refrigeration cycles, the unit that cools the room is inside, while the unit that discharges heat is installed outside. There is insulation between the outdoor unit and the air conditioner to prevent heat interference with the outside, but this experiment lacked such measures, so heat interference could have caused errors. Furthermore, as this is an experiment to maintain a steady state, there are limitations on the duration of the experiment for each group,
