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A heat exchanger is a device which is used to transfer heat between a no. of fluids, which is either separated by a solid wall or may be in direct contact with each other. It has a broad application in different industries including refrigeration and air conditioning, internal combustion engine, power plants, sewage treatment, etc.1
On the basis of flow arrangement, a heat exchanger is classified into the following main categories:
- Parallel flow heat exchanger
- Counter flow heat exchanger
- Cross flow heat exchanger
The fluid enters through the same end in a parallel flow heat exchanger and travels adjacent to each other in a parallel manner in the same direction, while in the counter flow heat exchanger, two fluids move in opposite direction to each other. It is the most efficient among the three exchangers. In the cross-flow heat exchanger, as the name suggests, fluid travels cross (roughly perpendicular) to each other.2
The main objective of this experiment is to determine the performance test and calculate the heat transfer rate, LMTD, and effectiveness of a heat exchanger in a parallel and counter flow heat exchanger.
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Materials: Heat Exchanger
Valves for flow and direction control- 5 pcs.
Thermometers- 4 pcs.
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First of all, start the water supply, keep the flow rate above 2.5 Lit/min (max. up to 7 Lit/min) for hot water and between 3 to 8 Lit/min for cold water. Place the thermometer in the pockets and switch ‘ON’ the geyser. Note down the readings after the temperature gets steady. Now, repeat the experiment by changing the water flow rate, and open valves V2 and V3, and close V1 and V4 for counterflow arrangement. Now, wait till a steady state is achieved, and note down the readings.
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The process of finding the heat transfer rate, heat transfer coefficients, LMTD and effectiveness of heat exchanger for both parallel and counter flow heat exchanger has been discussed. Be sure of keeping the steady water flow rate and temperature before noting down the readings to get accurate results.3
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- N. H. M. S. Francis Agyenim, “A review of materials, heat transfer and phase change problem formulation for latent heat thermal energy storage systems (LHTESS),” Renewable and Sustainable Energy Reviews, vol. 14, no. 2, pp. 615-628, 2010.
- Z. D. X. Z. S. S. Changhong Zhan, “Comparative study of the performance of the M-cycle counter-flow and cross-flow heat exchangers for indirect evaporative cooling – Paving the path toward sustainable cooling of buildings,” Journal of Energy, vol. 36, no. 12, pp. 6790-6805, 2011.
- R. J. G. T. H. Kuehn, “An experimental and theoretical study of natural convection in the annulus between horizontal concentric cylinders,” Journal of Fluid Mechanics, vol. 74, no. 4, pp. 695-719, 1976.