Shell and tube, and double pipes heat exchangers are examples of common exchangers using counter flow configurations. The best design for shell and tube and double-pipe exchanger is counter flow configuration, and the heat transfer between the fluid is the maximum. 18.5.1Simplified Counterflow Heat Exchanger (With Uniform Wall Temperature) To address this we start by considering the general case of axial variation of temperature in a tube with wall at uniform temperature and a fluid flowing inside the tube (Figure 18.12). Figure 18.12:Fluid temperature
Why is a counter flow heat exchanger better than a parallel flow heat
For example, heat exchanger designs can employ multiple flow passes and arrangements (e.g., both counter flow and crossflow arrangements) within a single heat exchanger. These types of heat exchangers are typically used to accommodate the limitations of an application, such as space, budget costs, or temperature and pressure requirements. Counter Flow Heat Exchanger In counter flow heat exchangers the fluids enter the exchanger from opposite ends. The counter flow design is most efficient, in that it can transfer the most heat from the heat transfer medium. % % Co u n t er %F l o w %H E %!!!!! = 1 F ! " # F! " # 1 F !! 1 F !!! " # F! " # 1 F !!!! Ph ase%Ch an ge%!! = ! !! ¿ ! !!
Types of Heat Exchangers. 1. Double - Pipe Heat Exchanger. A double-pipe heat exchanger is the simplest type of heat exchanger and can operate with co-current (Figure 1) or counter-current (Figure 2) flow. The design consists of a single small pipe (tube-side) inside of a larger one (shell-side). The Counterflow Heat Exchanger A counterflow heat exchanger has the hot fluid entering at one end of the heat exchanger flow path and the cold fluid entering at the other end of the flow path. Counter flow is the most common type of liquid-liquid heat exchanger, because it is the most efficient.
Illustration of a counter flow heat exchanger Download Scientific
Example: Calculation of Heat Exchanger Consider a parallel-flow heat exchanger, which is used to cool oil from 70°C to 40°C using water available at 30°C. The outlet temperature of the water is 36°C. The rate of flow of oil is 1 kg/s. The specific heat of the oil is 2.2 kJ/kg K. The overall heat transfer coefficient U = 200 W/m2 K. For example, in some applications steam is injected into water in order to heat it up. Some common applications where a heat exchanger is used are: refrigeration, air conditioning, space heating, and power plants, to name a few. There are of course many more.
Counter flow heat exchanger- When the fluids flow in opposite direction relative to each other, then the heat exchanger will be referred to as counter flow heat exchanger. We can find the effectiveness of the heat exchanger using the formula discussed in the later sections of this article. b] For counter flow heat exchanger:- ɛcounter = N T U 1 + N T U ɛ c o u n t e r = N T U 1 + N T U Effectiveness: The effectiveness of the heat exchanger is in the ratio of actual heat transfer to the maximum heat transfer. ∴ ɛ = Qactual Qmax ∴ ɛ = Q a c t u a l Q max Numerical on NTU method:
Schematic of counter flow microchannel heat exchanger Download
Cross flow heat exchangers are called the type of heat exchangers which have 90 degree angles for the direction of the fluids. Totally, it is hard to find a specific exchanger using cross flow configuration, but generally, Plate, shell and tube, one-phase, and multi-phase exchangers can be categorized as cross flow heat exchangers. Examples are automobile radiators, condenser coil in the refrigerator, air conditioner, solar water heater, chemical industries, domestic boilers, oil coolers in a heat engine, milk chillers in pasteurizing plant. Classification of heat exchangers: 1. Classification according to construction: Tubular heat exchangers. Plate heat exchangers.
An everyday example of a heat exchanger is the combustion engine of a car, where cooling fluid passes through inside the coils of a radiator as outside air moves around the radiator.. The other main type of heat exchanger is called a counter-flow heat exchanger, in which the two fluids move in opposing directions.. The counter-flow heat exchanger has three significant advantages over the parallel flow design. First, the more uniform temperature difference between the two fluids minimizes the thermal stresses throughout the exchanger. Second, the outlet temperature of the cold fluid can approach the highest temperature of the hot fluid (the inlet temperature).
Counter flow and parallel flow heat exchangers Newsfabs
There are three primary classifications of heat exchangers according to their flow arrangement. In parallel-flow heat exchangers, the two fluids enter the exchanger at the same end, and travel in parallel to one another to the other side. In counter-flow heat exchangers the fluids enter the exchanger from opposite ends. The counter current design is the most efficient, in that it can transfer. So let's take an absurdly simplified example. Let's assume we have a perfectly efficient, infinitely long heat exchanger with the same substance on each side, but one enters at 100 F and the other at 0 F. They both exit at 50 F (or very, very near that). The cooling relationship is logarithmic.