Explain vapour compression refrigeration (for dry saturated state of refrigerant) cycle with the help of P-h and T-s charts.
Processes in VCR cycle 1) The point 1 represents condition of refrigerant at entry of compressor which is wet. Process 1 – 2 – Isentropic compression of refrigerant vapour till it becomes dry and saturated. Process 2 – 3 – Condensation of vapour refrigerant up to saturated liquid condition at constant pressure. Process 3 – 4 – Expansion of liquid refrigerant by expansion device. This reduces pressure as well as temperature of liquid refrigerant. Process 4 – 1 – Evaporation of liquid refrigerant in the evaporator thus establishing required refrigerating effect. Thus it completes one cycle of refrigeration. Refrigerating effect = RE = m (h1 – h4) Compressor power = m (h2 – h1) Where m = mass flow rate of refrigerant in kg/sec.
