a explain various types of methods of

Question

(a) Explain various types of methods of refrigeration.

(b) Write the factors consideration for the selection of refrigerant for a system.

A 5 tonne refrigerating machine operating Bell Coleman cycle has an upper limit of pressure of 12 bar. The pressure and temperature at the start of the compression are 1 bar and 17^oC respectively. The compressed air cooled at constant pressure to a temperature of 40^oC enters the expansion cylinder.

Assuming both the expansion and compression processes to be isentropic with λ = 1.4; Determine

(i) C.O.P.

(ii) Piston displacement of compressor and expender.

(iii) Quantity of air in circulation per minute

(iv) Bore of compressor and expansion cylinders.

The unit run at 250 r.p.m. and is double acting. Stroke length is 200 mm.

(v) Power required to drive the Unit.

Take C_p = 1KJ/K_gK; C_v = 0.71 KJ/Kgk; R = 0.287 Kj/KgK