The type of liquor circulation system to be ' employed in evaporators (viz. natural or forced circulation) is determined mainly by the __________ of the liquid.

The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ΔT) between wall and outside bulk. The proportionality is given as

With increase in temperature, the total emissivity of conductors

In a forward feed multiple effect evaporator unit

If air (a non-condensing gas) is present in a condensing vapor stream, it will __________ the condensation rate of vapor.

Loss of heat from untagged steam pipe to the ambient air is by

View factor is important in heat transfer by

Arithmetic mean area can be used in heat transfer problem to calculate the heat flow by conduction through a cylinder which is

In case of heat flow by conduction for a cylindrical body with an internal heat source, the nature of temperature distribution is

In SI units, fouling factor is expressed in

Film boiling is usually not desired in commercial equipments, because

A sphere of radius 'R₁' is enclosed in a sphere of radius 'R₂'. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is

Thermal diffusivity is the most important in heat transfer by

Overall heat transfer co-efficient of a particular tube is U₁. If the same tube with some dirt deposited on either side has coefficient U₂, then

The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are

Prandtl and Reynold's analogies are identical for Prandtl number value of

Fruit juice (a heat sensitive material) can be concentrated in a __________ evaporator.

Tubes are held between top and bottom tube sheets in Calenderia type evaporator by keeping

The advantage of using a 1 - 2 shell and tube heat exchanger over a 1 - 1 shell and tube heat exchanger is

Three solid objects of the same material and of equal mass-a sphere, a cylinder (length = diameter) and a cube are at 500°C initially. These are dropped in a quenching bath containing a large volume of cooling oil each attaining the bath temperature eventually. The time required forchange in temperature is the smallest for

For heat flow through very thick walled cylinder, use____mean radius.

An ejector is used to

For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is

For a laminar flow of fluid in a circular tube, 'h₁' is the convective heat transfer co-efficient at velocity 'V₁'. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is

(N_Gr x N_Pr) is called the __________ number.

In SI units, thermal conductivity is expressed in

The critical radius 'r' of insulation on a pipe is given by

Heat transfer rate described by Fourier's law will decrease, if the __________ increases.

Nusselt number is the ratio of the

The outlet temperature of cooling water in a heat exchanger is generally not allowed to exceed above 50°C in industrial practice mainly to avoid

Tube expansion allowances exist in __________ heat exchanger.

For a multipass shell and tube heat exchanger, the LMTD correction factor is always

Overall heat transfer co-efficient for cooling of hydrocarbons by water is about

The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat exchanger is

Water is normally used as a coolant in the heat exchange equipments mainly because ofits

Indirect contact heat exchangers are preferred over direct contact heat exchangers, because

The Grashoff number is defined as the ratio of the

Absorptivity of a perfect black body is unity. Which of the following has maximum absorptivity ?

Which of the following is the most controlling factor for the rate of bubble detachment from the hot solid surface ?

Extremely large or small volumes of fluids are generally best routed through the shell side of a shell and tube heat exchanger, because of the

In which mode of heat transfer, the Biot number is important ?

The variation of thermal conductivity of a metal with temperature is often correlated using an expression of the form K = K₀ + at. where, K is the thermal conductivity and T is the temperature (in °K). The units of 'a' in SI system will be

The main purpose of providing fins on heat transfer surface is to increase the

A dephlegmator is a

Boiling point of a solution according to Duhring's rule is a linear function of the __________ of water.

As per Kirchoffs law, the ratio of the total radiating power to the absorptivity of a body depends on the

A black body does not __________ radiation.

Prandtl number is the ratio of

Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger ?

In evaporators, lowering the feed temperature