Heat Transfer, Refrigeration and Air Conditioning Online Test – Multiple Choice Questions and Answers 1. The index which corelates the combined effects of air temperature, relative humidity and air velocity on the human body, is known as mean radiant temperature effective temperature dew point temperature none of these 2. The freezing point of R-12 is -107.7°C -86.6°C -135.8°C -95.2°C 3. The alignment circle is marked on the psychrometric chart at 26°C DBT and 50% RH 26°C DBT and 60% RH 20°C DBT and 50% RH 20°C DBT and 60% RH 4. The condition of refrigerant after passing through the expansion or throttle valve, in a vapour compression system is high pressure saturated liquid very wet vapour wet vapour dry vapour 5. Thermal conductivity of a material may be defined as the heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces quantity of heat flowing in one second through a slab of the material of area 1 cm2 and thickness 1 cm when its faces differ in temperature by 1° C quantity of heat flowing in one second through one cm of material when opposite faces are maintained at a temperature difference of 1° C all of the above 6. The ratio of Nusselt number and the product of Reynold’s number and Prandtl number is equal to Peclet number Biot number Stanton number Grashoff number 7. The radiation emitted by a black body is known as full radiation total radiation black radiation all of these 8. The capillary tube is not used in large capacity refrigeration systems because cost is too high it is made of copper capacity control is not possible required pressure drop can not be achieved 9. Reynolds number is the ratio of energy transferred by convection to that by conduction kinematic viscosity to thermal diffusivity inertia force to viscous force none of the above 10. A good refrigerant should have high specific volume and high latent heat of vaporisation high operating pressures and low freezing point high latent heat of vaporisation and low freezing point low C.O.P. and low freezing point Loading … Question 1 of 10
