10,000 kg/hr of an aqueous feed containing 1% dissolved solids is to be concentrated to 20% solids, in a single effect evaporator. The feed enters at 25^{o}C. The steam chest is fed with saturated steam at 110^{o}C. The absolute pressure maintained in the evaporator is such that the water will boil at 55^{o}C. The heat transfer area available is 50 m^{2}. The boiling point elevations are as follows:
Feed: 0.2^{o}C
20% solution: 15^{o}C
The overall heat transfer coefficient, under normal operating conditions would be 2500 W/m^{2}.^{o}C
Estimate the heat load on the condenser, assuming no sub cooling of condensate.
A light motor oil with the following characteristics is to be heated from 65 to 120^{o}C in a 6 mm id pipe of 5 m long. The pipe is at 175^{o}C. How much oil can be heated in this pipe in kg/hr? What coefficient can be expected?
Data for the oil:
Thermal conductivity = 0.142 W/m.^{o}C
Specific heat = 2 kJ/kg.^{o}C
Viscosity (Temperature ^{o}C): 6.0 (65) ; 3.3 (120) ; 1.37 (175) cP
A thermopane window consists of two sheets of glass each 6 mm thick, separated by a layer of stagnant air also 6 mm thick. Find the percentage reduction in heat loss from this pane as compared to that of a single sheet of glass 6 mm thickness. The temperature drop between inside and outside remains same at 15^{o}C. Thermal conductivity of glass is 30 times that of air.
An asbestos pad, square in crosssection, measures 0.05 m on a side and increases linearly to 0.1 m on the side at the other end (see the figure). The length of the pad is 0.15 m.
If the small end is held at 600 K and the larger end at 300 K. What will be the heat flow rate if the other four sides are insulated. Assume one directional heat flow. Thermal conductivity of asbestos is 0.173 W/m.K.
The outside surface temperature of a pipe ( radius = 0.1m ) is 400 K. The pipe is losing heat to atmosphere, which is at 300 K. The film heat transfer coefficient is 10 W/(m^{2}.K). To reduce the rate of heat loss, the pipe is insulated by a 50 mm thick layer of asbestos ( k = 0.5 W/(m.K) ). Calculate the percentage reduction in the rate of heat loss.
In a 1  1 counter flow shell and tube heat exchanger, a process stream (C_{P} = 4.2 kJ/(kg.K) ) is cooled from 450 to 350 K using water ( C_{P} = 4.2 kJ/(kg.K) ) at 300 K. The process stream flows on the shellside at a rate of 1 kg/s and the water on the tubeside at a rate of 5 kg/s. If the heat transfer coefficients on the shell and tube sides are 1000 W/(m^{2}.K) and 1500 W/(m^{2}.K), respectively, determine
(a) the required heat transfer area.
by what factor will the required area change if the flow is concurrent?
Neglect tube wall resistance and fouling resistances.
An aqueous solution of a solute is concentrated from 5% to 20% (mass basis) in a singleeffect shorttube evaporator. The feed enters the evaporator at a rate of 10 kg/s and at a temperature of 300 K. Steam is available at a saturation pressure of 1.3 bar. The pressure in the vapor space of the evaporator is 0.13 bar and the corresponding saturation temperature of steam is 320 K. If the overall heat transfer coefficient is 5000 W/(m^{2}.K), calculate the
(a) steam economy
(b) heat transfer surface area.

Enthalpy (kJ/kg) 
Heat of vaporization (kJ/kg) 
Saturated steam (1.3 bar; 380 K) 
 
2000 
Saturated steam (0.13 bar; 320 K) 
2200 
 
Feed (5% ; 300 K) 
80 
 
Concentrated liquor (20% ; 325 K) 
400 
 
Boiling point elevation is 5 K.
A thermocouple junction may be approximated as a sphere of diameter 2 mm with thermal conductivity 30 W/(m.^{o}C), density 8600 kg/m^{3} and specific heat 0.4 kJ/(kg.^{o}C). The heat transfer coefficient between the gas stream and the junction is 280 W/(m^{2}.^{o}C). How long will it take for the thermocouple to record 98 percent of the applied temperature difference?
A shell and tube steam condenser is to be constructed of 2.5 cm O.D., 2.2 cm I.D., single pass horizontal tubes with steam condensing at 54^{o}C on the outside of the tubes. The cooling water enters at 20^{o}C and leaves at 36^{o}C at a flow rate of 1 kg/s. The heat transfer coefficient for the condensation of steam is 7900 W/(m^{2}.^{o}C). Calculate the tube length. If the latent heat of condensation is 2454 kJ/kg, calculate the condensation rate per tube. The properties of water are as follows:
Specific heat 4180 J/(kg.^{o}C)
Viscosity 0.86 x 10^{3} kg/(m.s)
Thermal conductivity 0.61 W/(m.^{o}C)
The heat transfer coefficient for turbulent flow in a pipe may be determined by
Nu = 0.023 Re^{0.8} Pr^{0.4}
A Rocket chamber can be assumed as a spherical steel chamber 30 cm dia. Within this fuel burns at a temperature of 1500^{o}C. In order to protect the wall and reduce heat transfer a 5 cm aluminabrick layer (K = 3.5 W/m.K) is provided inside and two insulation layers (3 and 5 mm thick, and respective K's are 0.17 and 0.85 W/m.K) outside the chamber. Find out heat loss and intermediate wall temperatures when surrounding temperature was 100^{o}C. If the insulation layers are reversed will there be any effect on heat transfer and interface temperatures?
A steel sphere is of inner radius 40 cm and outer radius 45 cm is used to store liquid oxygen (B.P is minus 183^{o}C). The sphere is covered with one layer of insulation whose K is 0.35 W/m.K and another insulation whose K is 0.098 W/m.K. The sphere is exposed to atmosphere of 25^{o}C. Find out the rate of oxygen becoming vapor every minute. Latent heat of oxygen is 370 kJ/kg.
A steam pipe 160 mm id and 170 mm od is covered with two layers of insulation. The thickness of the first layer is 30 mm and that of the second is 50 mm. The thermal conductivity values are 50, 0.15 and 0.08 kcal/m.hr.^{o}C for the pipe, first insulation and second insulation respectively. The temperature of the inner surface of the steam pipe is 300^{o}C and that of the outer surface of the insulation layer is 50^{o}C. Determine the quantity of heat lost per meter length of steam pipe and the layer contact temperatures.
Brick work of a furnace is built of layers of fire clay and red brick and the space between them is filled with common brick. Fire clay layer is 120 mm thick, common brick is 50 mm thick and the red brick layer is 250 mm thick. The thermal conductivity values for the materials are 0.93, 0.13 and 0.7 kcal/hr.m.^{o}C respectively. Find the thickness of the red brick layer if the common brick layer is to be absent and the heat transfer remains the same. Take the fir clay thickness also remains the same.
A heat exchanger heats 25,000 kg/hr of water entering at 80^{o}C while cooling 20,000 kg/hr of water from 100^{o}C to 80^{o}C. Determine the heat transfer area necessary for (i) Parallel flow arrangement (ii) Counter flow arrangement. Given Overall heat transfer coefficient, U= 1,500 W/m^{2} K
A brick wall of thermal conductivity 1.0 W/m.K is of 300 mm thickness, lined on the inner face with plaster of thermal conductivity 0.4 W/m.K and thickness 20 mm. If a temperature difference of 70 K is maintained between the two outer faces, what is the heat flow per unit area of the wall?