Heat Exchanger
Thermal Design and Optimization
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Thermal Design and Optimization of Heat Exchanger
A heat exchanger is a system used to transfer heat between two or more fluids. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural-gas processing, and sewage treatment.
The heat exchanger is a major element as far as heat transfer and energy conservation are concerned. There are so many types of heat exchangers available but due to the wide range of design possibilities, simple manufacturing, low maintenance cost, cross flow and counter flow heat exchangers are extensively used in petroleum, petrochemical, air conditioning, food storage, and other industries. The shell and tube heat exchanger is widely used in industries as a chiller plant for transferring waste heat from the injection moulding machine to the cooling water to improve the efficiency of the injection moulding machine. The transformations of the waste heat from the injection moulding machine to the cooling water are dependent on the heat exchange capacity of heat exchangers. To increase the heat exchange capacity of the heat exchanger optimization is done which seeks to identify the best parameter combination of heat exchangers. The prefix parameter (tube diameter) is used as an input variable and the output parameter is the maximum temperature difference between the shell and tube heat exchanger. Nine models are made on the basis of Taguchi method in NX 10.00 and CFX analysis is carried out in ANSYS 14.5. Result obtained from that gives the best dimension of the heat exchanger for minimum outlet temperature of the water.
Fouling is an inevitable phenomenon in shell and tube heat exchangers. Even though regular water has considered a working fluid in the shell and tube heat exchanger, it has a significant impact on thermal and hydronic performance due to fouling properties. The amount of layer deposition has a direct impact on heat transfer and pressure drop, as it affects on the physical dimension of the shell and tube heat exchanger. The heat transfer surface fouls during operation, resulting in increased thermal resistance and often an increase in the pressure drop and pumping power. It is required to understand, how mass flow rate can affect on the deposition rate of the fouling layer inside the tube. In this part of the work, the study has been conducted to evaluate the optimal operating condition that leads to a lower fouling deposition rate inside the heat exchanger while keeping in mind thermal and hydraulic requirements.
This work is intended to assist anyone with some general technical experience, but perhaps limited specific knowledge of heat transfer equipment. A characteristic of heat exchanger design is the procedure of specifying a design, heat transfer area and pressure drops and checking whether the assumed design satisfies all requirements or not. The purpose of this work is how to design the shell-and-tube heat exchanger which is the majority type of liquid-to-liquid heat exchanger. General design considerations and design procedures are also illustrated in this paper. In design calculation, HTRI software is used to verify manually calculated results. In this research, work attempt is made to overcome some major theoretical assumptions and serve a practical approach as much as possible for shell tube heat exchanger design. It is hoped that the software will bridge the gap between engineering fundamentals and the existing industry practice of shell and tube heat exchanger design.
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