ISRO Scientist or Engineer Refrigeration & Air-Conditioning 2013
For the following questions answer them individually
A solar energy based heat engine which receives 80 kJ of heat at 100 deg Cand rejects 70 kJ of heat to the ambient at 30 deg Cis to be designed. The thermal efficiency of the heat engine is
The temperature variation under steady heat conduction across a composite slab of two materials with thermal conductivities K1 and K2 is shown in Figure. Then, which one of the following statements holds?
What is the value of the view factor for two inclined flats having common edge of equal width, and with an angle of 20 degrees?
A 2 kW, 40 litre water heater is switched on for 20 minutes. The heat capacity $$C_p$$ for water is 4.2 kJ/kg-K. Assuming all the electrical energy has gone into heating the water, increase of the water temperature in degree centigrade is
Heat is being transferred by convection from water at $$48^\circ C$$ to a glass plate whose surface that is exposed to the water is at 40°C. The thermal conductivity of water is 0.6 W/m-K and the thermal conductivity of glass is 1.2 W/m-K. The spatial gradient of temperature in the water at the water-glass interface is $$\frac{dT}{dy} = 1 \times 10^4 k/m$$
The value of the temperature gradient in the glass at the water-glass interface in K/m is:
A p-v diagram has been obtained from a test on a reciprocating compressor. Which of the following represents that diagram?
A small copper ball of 5 mm diameter at 500 K is dropped into an oil bath whose temperature is 300 K. the thermal conductivity of copper is 400 W/m-K, its density 9000 kg/m$$^3$$ and its specific heat 385 J/kg-K, if the heat transfer coefficient is 250 W/m$$^2$$-K and lumped analysis is assumedto be valid, the rate of fall of the temperature of the ball at
the beginning of cooling will be, in K/s,
A Carnot cycle operates between the temperatures limits of 300 K and 2000 K, and produces 600 kW of net power. The rate of entropy change of the working fluid during the heat addition process is:
Hot oil is cooled from 80 to $$50^\circ C$$ in an oil cooler which usesair as the coolant. The air temperature rises from 30 to $$40^\circ C$$. The designer uses a LMTD value of $$26^\circ C$$. The type of heat exchanger is
Two bodies A and B having equal surface areas are maintained at 100 and 200. The thermal radiation emitted in a given time by A and B arein the ratio:
