Heat Exchanger Analysis through NTU Method for Different Material

A new effectiveness-NTU method is developed for a special type of heat exchangers, in which the fluid of a passage is in simultaneous thermal contact with two separate fluids flowing in the opposite direction. An extensive amount of numerical simulations are carried out by a kerative method for wide ranges of dimensionless parameters such as ratios of capacity rates, NTUs, or a dimensionless inlet temperature. The large body of resulting data are then effectively reduced to a small number of simple equations and graphs by introducing a new effectiveness, c. s is defined as the ratio of actual heat transfer to the maximum heat transfer obtained when the NTUs become very large while the ratio of two NTUs is kept constant. The developed method is readily applicable to the cycle analysis and design, in the same way as the:-NTU method for the usual double-passage heat exchangers. A cross-flow heat exchanger is used in a cooling and ventilation system that requires heat to be transferred from one airstream to another. A cross-flow heat exchanger is made of thin metal panels, normally aluminium. The thermal energy is exchanged via the panels. A traditional cross-flow heat exchanger has a square cross-section. It has a thermal efficiency of 40–65%. A counter-flow or dual cross-flow heat exchanger can be used if greater thermal efficiencies are required – typically up to 75–85 %. In some types of exchanger, humid air may cool down to freezing point, forming ice. A cross-flow is typically less expensive than other types of heat exchanger. It is normally used where hygienic standards require that both airstreams are kept completely separate from one another. It is often used in heat recovery installations in large canteens, hospitals and in the food industry. Unlike a rotary heat exchanger, a cross-flow heat exchanger does not exchange humidity.