Refrigration lecture for free to dow.pptx

بعتل

1. Gas Refrigeration CYCLES Osama Hamed 2019-2020

2. What is meant by “Refrigeration”? Refrigeration is the process of removing heat from an enclosed space or from a substance for the purpose of lowering its temperature. Mechanical Cooling Processes Gas Cycle Refrigeration . Mechanical Vapor Compression Refrigeration Absorption Refrigeration. Solar Energy Based Refrigeration Systems Steam Jet Refrigeration System Thermoelectric Refrigeration Systems Vortex Tube

3. Heat Engine and Reversed Heat Engine High-temperature reservoir at T H Low-temperature reservoir at T L Heat Engine Q H Q L W Heat Engine High-temperature reservoir at T H Low-temperature reservoir at T L Reversed Heat Engine Q H Q L W Reversed Heat Engine

4. Carnot Cycle and Reversed Carnot Cycle 1–2 isothermal heat addition 2–3 isentropic expansion 3–4 isothermal heat rejection 4–1 isentropic compression 1–2 isentropic expansion 2–3 isothermal heat absorption 3–4 isentropic compression 4–1 isothermal heat rejection

5. Gas Refrigeration Cycles Joule or Reversed Brayton or Bell–Coleman Cycle 1–2 isentropic compression 2–3 isobaric heat rejection 3–4 isentropic expansion 4–1 isobaric heat absorption

6. - Bell–Coleman Cycle Gas Refrigeration Cycles

7. Refrigeration load is the rate at which heat must be removed from a refrigerated space in order to maintain a desired temperature Ton of refrigeration  is the rate of heat removal required to freeze one ton  of water at 0°C in 24 hours. 1 Ton Refrigeration = (1000 kg) (303.89kJ/kg) / (24 hr)     = 12662 kJ/hr/(3600 s/hr)= 3.517 kW 1Ton Refrigeration (TR) = 3.517 kW=12000 Btu/h Refrigeration effect is the difference in specific enthalpy across the evaporator Definitions

8. -Effect of pressure ratio on COP of the Bell-Coleman cycle

9. Actual Bell–Coleman Cycle Isentropic efficiency of the compressor and the expander

10. Joule Cycle improvements Regenerative Joule Cycle Heat Exchanger Effectiveness