Dimensionless time is represented by

Fins are made as thin as possible to

The product of buoyant force and inertia force to the square of the viscous force is

In order to achieve maximum heat dissipation, the fin should be designed in such a way that:

Consider the following statements pertaining to large heat transfer rate using fins:

1. Fins should be used on the side where heat transfer coefficient is small.

2. Long and thick fins should be used.

3. Short and thin fins should be used.

4. Thermal conductivity of fin material should be large.

Which of these statements are correct?

A thermocouple in a thermowall measures the temperature of hot gas flowing through the pipe. For the most accurate measurement of temperature, the thermowall should be made of

Match List – I with List – II and select the correct answer using the codes given below the lists:

Consider the following statements:

1. The efficiency of heat transfer in a condenser will improve by increasing  the overall heat transfer coefficient.

2. The efficiency of heat transfer in a condenser will improve by increase of the velocity of flow of water in the tube.

3. The difference between the temperature of steam entering the condenser and the inlet water temperature should be maximum for maximum efficiency.

Which of the above statements are correct?

A cross-flow type air heater has an area of 50 m². The overall transfer coefficient is 100W|m² K; and heat capacity of the stream, be it hot or cold, is 1000 W/K. What is the NTU?

The effectiveness of a counter-flow heat exchanger has been estimated as 0.25. Hot gases enter at 200⁰C and leave at 75⁰C. Cooling air enters at 40⁰C. The temperature of the air leaving the unit will be

Statement (I) : A counter flow heat exchanger is more effective than a parallel flow heat exchanger.

Statement (II) : For same temperature limits of hot and cold fluids, the overall heat transfer coefficient of counter flow heat exchanger is more than parallel flow heat exchanger.

The characteristic length for computing Grashof number in the case of horizontal cylinder is

In a concentric double-pipe heat exchanger where one of the fluids undergoes phase change

The fouling factor in heat exchanger is defined as

The correct sequence for different types of heat exchangers in the decreasing order to effectiveness is

What does NTU indicate?

Floating heads are provided in heat exchangers to

Match List – I with List – II and select the correct answer using the codes given below the lists:

For a balanced counter flow heat exchanger, the temperature profiles of the two fluids are

In a balanced counter flow heat exchanger with ${\stackrel{•}{m}}_h{c}_h={\stackrel{•}{m}}_c{c}_c$, the NTU is equal to 1.0. What is the effectiveness of the heat exchanger?

The ‘NTU’ (Number of Transfer Unit) in a heat exchanger is given by which one of the following?

Conduction as well as fluid motion is

Which of the following is an example of natural convection?

Which of the following is an example of forced convection

Which of the following is an effective way of producing forced convection in liquid bath?