Fouling is defined as the formation of undesired deposits on heat transfer surfaces, which increase the resistance to fluid flow, resulting in higher pressure drop and reduced heat transfer. The growth of deposits causes the thermohydraulic performance of heat exchanger to degrade over time. Fouling affects the energy consumption and therefore increases the amount of extra material or fuel required to generate the required amount of heat transfer.

Basics of corrosion

Most common metals and their alloys are attacked by environments such as atmosphere, soil, water, or aqueous solutions. This destruction of metals and alloys is known as corrosion.

It is generally agreed that metals are corroded by an electrochemical mechanism. With practically all commercial processes engineered on a continuous basis of operation, premature failure from corrosion of various types of equipment, including heat exchangers, piping, and others, may mean costly shut downs and expensive maintenance operations.

Classification of heat exchangers according to flow direction
According to the direction of the flow heat exchangers can be classified as follows:
1) Counterflow;
2) Crossflow;
3) Parallel flow.

In counteflow type of heat exchangers, the two fluids flow parallel to each other, but in opposite directions. This is one of the most efficient configurations for single-pass arrangements.

Classification of heat exchangers according to transfer process

According to transfer process heat exchangers can be divided into 2 major categories:
1) Indirect contact type;
2) Direct contact type.

Indirect Contact Type Heat Exchangers

In this type of heat exchangers, the fluid streams remain separate, and the heat transfer takes place continuously through a separating wall. There is no direct mixing of the fluids because each fluid flows in separate fluid passages.

Evolution of Plate Heat Exchangers

Since the introduction in the 1920s for commercial usage plate-and-frame heat exchangers has evolved over the last several decades and various modifications were developed. Some of these modifications were driven by new strategies for making more compact equipment, some focused on overcoming disadvantages of PHEs, others on expanding the applications spectrum. That resulted mostly in variations of corrugation patterns of plate’s surfaces and altered construction.

Pressure Drop


Fluids need to be pumped through the heat exchanger in most applications. It is essential to determine the fluid pumping power required as part of the system design and operating cost analysis.

The fluid pumping power is proportional to the fluid pressure drop, which is associated with fluid friction and other pressure drop contributions along the fluid flow path. The fluid pressure drop has a direct relationship with heat transfer, operation, size mechanical characteristics, and other factors including economic considerations.

Wort Cooling Systems

Wort cooling systems are employed to bring the wort to a temperature suitable for fermentation. Closed systems with plate heat exchangers have been used for several decades to prevent the danger of infection and energy loss.

Wort cooling systems extract heat from the wort and generate hot water, brine, and propylene glycol solutions, as well as direct expansion of ammonia.

Principles of Heat Transfer

To understand how heat losses occur and how they can be minimized needed to understand the principles of heat transfer. Heat transfer finds application in equipment sizing as well. For instance, a heat exchanger is used to transfer heat load from one fluid to another. Thus, heat transfer applications are involved with energy transfer in equipment, piping systems, and building design.

Heat transfer is determined by the effects of conduction, radiation and convection.