Heat Transfer Refrigeration and Airconditioning

The C.O.P. of a refrigerator working on a reversed Carnot cycle is (where T1 = Lowest absolute temperature, and T2 = Highest absolute temperature)
A. `(T_1)/(T_2 - T_1)`
B. `(T_2 - T_1)/(T_1)`
C. `(T_1 - T_2)/(T_1)`
D. `(T_2)/(T_2 - T_1)`


A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h1, h2 and h3 respectively. The average heat transfer coefficient for the cube is 

A. `h_1 + h_2 + h_3`
B. `(h_1 h_2 h_3)^(1//3)`
C. `1/h_1 + 1/h_2 + 1/h_3`
D. none of these


When tc1 and tc2 are the temperatures of cold fluid at entry and exit respectively and th1 and th2 are the temperatures of hot fluid at entry and exit point, and cold fluid has lower heat capacity rate as compared to hot fluid, then effectiveness of the heat exchanger is given by

A. `(t_(c1) - t_(c2))/(t_(h1) - t_(c1))`
B. `(t_(h2) - t_(h1))/(t_(c2) - t_(h1))`
C. `(t_(h1) - t_(h2))/(t_(h1) - t_(c1))`
D. `(t_(c2) - t_(c1))/(t_(h1) - t_(c1))`


The rate of heat flow through a body is`Q = (KA (T_1 - T_2))/(times)`  . The term`(T_1 - T_2)/(times)` is known as temperature gradient

A. Yes
B. No


The rate of heat flow through a body is `Q = (KA (T_1 - T_2))/(times)`. The term x/kA is known as

A. thermal coefficient
B. thermal resistance
C. thermal conductivity
D. none of these