International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 04 | Apr -2017
p-ISSN: 2395-0072
www.irjet.net
REVIEW ON ENHANCEMENT OF HEAT EXCHANGER BY USING CONICAL INSERT Sabale Sachin K1., Rohamare Kishor S2., Sanap Dattu S3., Mind Dattatraya B4. Asst. Prof. Sawant S. G5. 1,2,3,4BE Student, Department of Mechanical Engineering, SND COE & RC, Maharashtra, India 5Asst. Professor, Department of Mechanical Engineering, SND COE & RC, Maharashtra, India ---------------------------------------------------------------------***--------------------------------------------------------------------of the increased pumping power, several techniques have Abstract - The heat exchanger is an important device in been done in recent years and are discussed. Inserts like Conical tube a type of passive heat transfer augmentation techniques have shown significantly good results.
almost all of the mechanical industries it is key element. Thus many researchers in this area are working to improve the performance of the heat exchangers in terms of heat transfer rate. This paper is a review of passive augmentation techniques used in heat exchangers. The thermal performance behavior of tube in tube heat exchanger it is studied for wire coil inserts, twisted tape inserts and their combination. The research was done for constant/periodically varying wire coil pitch ratio. Some of them have varied 3 coil pitch ratios.
1.1 HEAT TRANSFER ENHANCEMENT Heat transfer enhancement is the process of modifying a heat transfer surface or the cross section flow to either increase the heat transfer coefficient between fluid and surface to effectively maintain higher heat loads with a smaller temperature difference. I have treated some practical examples of heat transfer enhancement like fins, surface roughness, conical inserts and coiled tube, which are generally referred to as passive techniques. Heat transfer enhancement may also be achieved by surface, fluid vibration, electrostatic fields. These methods are often referred to as active techniques because they required the application of external power. Active techniques have received attention in the research literature their some practical applications are very limited. In this section some specific example of passive techniques. Increases in heat transfer due to surface treatment increased turbulence, increased surface area, and improved mixing or flow swirl. These effects generally result in increase in pressure drop along with the more increase in heat transfer. However, with performance evaluation and optimization, significant heat transfer improvement relative to a untreated heat transfer surface of the same nominal heat transfer area is achieved for a variety of applications. The increasing in attractiveness of different heat transfer enhancement techniques are benefits of industrial importance because due to heat exchanger offer the opportunity. 1) To reduce the heat transfer surface area required for a given application. 2) Reduces the heat exchanger size and cost. 3) Increase the heat rate of the exchanger. 4) Permit closer approach temperature.
The conical ring were also been tested. These inserts are tested individually and in combine form and results were compared. The Reynolds number is selected for allowing the inserts to be tested for different flow conditions from laminar, transient and turbulent. The new improved performance was found in the increasing order for inserts like wire coil, twisted tapes and conical inserts. Also some of researchers have developed correlations for these inserts for nusselt number as a function of Reynolds number. Key Words: Heat transfer enhancement, Passive technique, wire coil, Heat exchanger, Conical insert.
1. INTRODUCTION
Heat exchangers are widely used in the fields of refrigeration, air conditioning, water cooler, space heating, automobile, radiator and chemical engineering. Fin-tube heat exchanger with two rows of round tubes is commonly used in refrigeration and air-conditioning systems. Heat exchanger devices such as plate type, plate fin type operate on the principle of temperature difference between two mediums and can find efficient sensible heat transfer from one fluid to another. With the development of design of heat exchanger and making some changes without affecting the cost, the heat transfer enhancement can be achieved. These techniques are also known as Heat transfer Enhancement or Improvement. Augmentation techniques increase convective heat transfer rate by reducing the thermal resistance in a heat exchanger. Use of Heat transfer enhancement techniques lead to increase in heat transfer coefficient but increase in pressure drop with increase in cost. So, while designing a heat exchanger using any of these techniques, synthesis of heat transfer rate &pressure drop has to be done. Together from this, issues like long term performance & detailed economic synthesis of heat exchanger has to be studied. To achieve more heat transfer rate in an existing or new heat exchanger while taking care
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All of these can be concern from the expression for heat rate for a heat exchanger. Q=UA LMTD any enhancement technique which increases the heat transfer coefficient also increases conductance U. One can reduce the heat transfer area A, increase the heat rate or decrease the temperature difference. LMTD, for fixed Q and LMTD, Fixed A and LMTD, or fixed Q and A. Enhancement can also be used to prevent the overheating of heat transfer surface with a fixed heat generation rate. In practical application a
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