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Energy Transport in Thermal Energy Systems
Published in Steven G. Penoncello, Thermal Energy Systems, 2018
Tables 5.3 and 5.4 show two entries for ε-NTU and NTU-ε functions for counter flow heat exchangers. One equation is for Cr < 1 and the other equation is for Cr = 1. If Cr = 1 both fluids have the same thermal capacity rate. It is possible for this situation to occur with two different fluids, but it is rather coincidental. However, this situation can occur in a heat exchanger where both hot and cold fluids are the same and they have the same mass flow rate. A common type of heat exchanger where this can occur is a regenerative heat exchanger. An example of a regenerative heat exchanger used in a gas turbine cycle is shown in Figure 5.18. In this figure, the heat exchanger labeled “regenerator” is a counter flow regenerative heat exchanger. In the cycle shown in Figure 5.18, the purpose of the regenerator is to preheat the air entering the combustion chamber by utilizing otherwise-wasted hot turbine exhaust gases. The result is a reduction in fuel requirement for the same power output resulting in an increased thermal efficiency.
Waste Heat Recovery
Published in Clive Beggs, Energy: Management, Supply and Conservation, 2010
In a regenerative heat exchanger a matrix of material is alternately passed from a hot fluid to a cold fluid, so that heat is transferred between the two in a cyclical process. The most commonly used type of regenerative heat exchanger is the thermal wheel, which has a matrix of material mounted on a wheel, which slowly rotates at approximately 10 revolutions per minute, through hot and cold fluid streams (as shown in Figure 11.8). The major advantage of a thermal wheel is that there is a large surface area to volume ratio resulting in a relatively low cost per unit surface area.
Study on spray condensation performance of desulfurization wet flue gas
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Lulu Li, Man Zhang, Xuan Yao, Zhe Zhao, Baoguo Fan, Yan Jin, Hairui Yang
According to the working principle, heat and mass exchange equipment can be divided into partition type, regenerative heat type, and direct-contact type. The cold and hot media of the partition heat exchanger continuously flow in their respective flow channels to complete the heat exchange without contacting or mixing with each other. In the regenerative heat exchanger, heat is transferred by means of a regenerator composed of fillers, and cold and hot fluids alternately flow through a channel composed of the regenerator, while hot fluids store heat in the regenerator and cold fluid flow through to absorb heat. On the contrast, in the direct-contact heat exchanger, the two fluids are mixed with each other in direct contact with high heat and mass transfer efficiency. Heat and mass exchange equipment can be divided into parallel flow type, counter flow type, cross flow type, and mixed type according to the flow direction of hot fluid and cold fluid, among which counter flow type has the largest average heat transfer temperature difference.