In most of the engineering applications, however, heat is transferred in successive steps by similar or different mechanisms. For instance, let us consider the case of heating of water in a tube laid in a heat exchanger (or cooling of hot fluid in shell by CW). The water will receive […]

Heat is the thermal energy transit from one system to another. The thermal energy can originate from any kind of energy according to the first law of thermodynamics. Transfer of heat is due to unique property of matter, temperature, and is governed by second law of thermodynamics, which dictates that […]

Two kind of heat transfer occur within the tower between warm water and air. Latent heat of vaporization: Some of the liquid changes to vapor with the absorption of heat. This energy, called the latent heat of vaporization, is that necessary to overcome the attractive forces between molecules in the […]

The rate at which heat is transferred in a cooling tower depends upon four factors: the area of the water surface in contact with air; the relative velocity of air and water; the time of contact between air and water; the difference between the wet bulb temperature of the inlet […]

The process represented in the above figure (1.1) is one in which hot fluid is cooled by water, which itself heated without any loss of exchanged heat. Industrial heat exchangers consist of a number of tubes enclose in a shell. Exchangers with cooling water in the tubes, and hot product […]

The general equation for heat transfer across a surface is: Q = UA Δtm                                                                                           (eq – 1.7) Where Q = heat transferred per unit time (W) U = the overall heat transfer coefficient (W/m2  oC) A –heat-transfer area, m2, Δtm = the mean temperature difference, the temperature driving force, oC. […]

The principal types of heat exchangers used in chemical and allied industries which will be discussed in this chapter, are listed below: Double-pipe exchanger: the simplest type, used for cooling and heating. Shell and tube exchangers: used for all applications Plate and frame exchangers (plate heat exchangers): used for heating […]

As the physical layout of the exchanger cannot be determined until the area is known the design of an exchanger is of necessity a trial and error procedure. The steps in a typical design procedure are given below: Define the duty: heat transfer rate, fluid flow-rates, temperatures. Collect together the […]

Before equation (eq – 1.7) can be used to determine the heat transfer area required for a given duty, an estimate of the mean temperature difference Δtm must be made. This will normally be calculated from the terminal temperature differences: the difference in the fluid temperatures at the inlet and […]

Estimation of the “true temperature difference” from the logarithmic mean temperature difference by applying a correction factor to allow for the departure from true counter-current flow: ΔT m = Ft ΔT tm                          (eq – 1.10) Where ΔT m = true temperature difference, the mean temperature difference for use in the […]