Q. Capacity ratio is defined as the product of

View solution

Q. Which of the following is not associated with heat exchanger?

View solution

Q. The engine oil at 150 degree Celsius is cooled to 80 degree Celsius in a parallel flow heat exchanger by water entering at 25 degree Celsius and leaving at 60 degree Celsius. Estimate the exchanger effectiveness

View solution

Q. In a surface condenser, the water flowing through a series of tubes at the rate of 200 kg/hr is heated from 15 degree Celsius to 75 degree Celsius. The steam condenses on the outside surface of tubes at atmospheric pressure and the overall heat transfer coefficient is estimated at 860 k J/m² hr degree. Find the effectiveness of the heat exchanger. At the condensing pressure, stream has saturation temperature 0f 100 degree Celsius and the latent heat of vaporization is 2160 k J/kg. Further, the steam is initially just saturated and the condensate leaves the exchanger without sub-cooling i.e. only latent heat of condensing steam is transferred to water. Take specific heat of water as 4 k J/kg K

View solution

Q. For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference for parallel flow is

View solution

Q. Water (specific heat = 4 k J/kg K) enters a cross flow exchanger (both fluids unmixed) at 15 degree Celsius and flows at the rate of 7.5 kg/s. It cools air (C P = 1 k J/kg K) flowing at the rate of 10 kg/s from an inlet temperature of 120 degree Celsius. For an overall heat transfer coefficient of 780 k J/m² hr degree and the surface area is 240 m², determine the NTU

View solution

Q. Pick the odd one out.

View solution

Q. A cross flow type air heater has an area of 50 cm². The overall heat transfer coefficient is 100 W/m² K and heat capacity of both hot and cold stream is 1000 W/m K. The value of NTU is

View solution

Q. After expansion from a gas turbine, the hot exhaust gases are used to heat the compressed air from a compressor with the help of a cross flow heat exchanger of 0.8 effectiveness. What is the number of transfer units of the heat exchanger?

View solution

Q. E – NTU method is particularly useful in thermal design of heat exchangers when

View solution

Q. The engine oil at 150 degree Celsius is cooled to 80 degree Celsius in a parallel flow heat exchanger by water entering at 25 degree Celsius and leaving at 60 degree Celsius. Estimate the number of transfer units

View solution

Q. In a surface condenser, the water flowing through a series of tubes at the rate of 200 kg/hr is heated from 15 degree Celsius to 75 degree Celsius. The steam condenses on the outside surface of tubes at atmospheric pressure and the overall heat transfer coefficient is estimated at 860 k J/m² hr degree. Find the number of transfer units of the heat exchanger. At the condensing pressure, stream has saturation temperature 0f 100 degree Celsius and the latent heat of vaporization is 2160 k J/kg. Further, the steam is initially just saturated and the condensate leaves the exchanger without sub-cooling i.e. only latent heat of condensing steam is transferred to water. Take specific heat of water as 4 k J/kg K

View solution

Q. NTU is a number of transfer units, dimensionless parameter defined as

View solution

Q. When two fluids of the heat exchanger are separated by a plane wall, the thermal resistance comprises
(i) Convection resistance due to the fluid film at the inside surface
(ii) Conduction resistance
(iii) Convection resistance due to the fluid film at the outside surface
Identify the correct option

View solution

Q. Figure represents the block diagram of a heat exchanger. There were some aspects in the design and performance analysis of a heat exchanger. Identify the correct one

View solution

Q. The heat loss from unpainted aluminum side of a house has been calculated on the presumption that overall coefficient of heat transfer is 5 W/m² K. Later, it was discovered that the air pollution levels are such that fouling factor on this side is of the order of 0.0005 m² K/W. Find overall heat transfer coefficient of dirty side

View solution

Q. What is the value of fouling factor for engine exhaust?

View solution

Q. What is the value of fouling factor for industrial liquids?

View solution

Q. After being in service for a period of six months, a heat exchanger transforms 10% less heat than it does what new. Determine the effective fouling factor in terms of its clean overall heat transfer coefficient. It may be presumed that the heat exchanger operates between the same temperature differentials and that there is no change in the effective surface area due to scale build up

View solution

Q. In a counter flow heat exchanger, water flowing through a tube of 10 cm inner diameter is heated by steam condensing on the outside of the tube. The convective film coefficient on the water and steam side are estimated to be 12000 and 20000 k J/m² hr degree. Neglecting tube thickness and its resistance to heat flow, workout the overall heat transfer coefficient for the heat exchanger

View solution