Some Facts Resulting from the Key Variables Used in the Description of the Recuperative Heat Exchangers

Abstract

There are the various types of heat exchangers. The selection of the heat exchanger right type is the first basic assumption for its optimal operation. The heat exchanger calculation itself is another prerequisite for its optimal operation. This article deals with the variables which are usually used to describe the stationary operation of any recuperative heat exchanger with two incoming and two outgoing streams. The knowledge of these variables, including the facts resulting from them, is necessary not only from the point of view of the calculation but also from the point of view of the evaluation of the experimental data of any heat exchanger. The variables values needed for the calculation of heat exchangers, so-called key variables, must always fall within the values range determined on the basis of generally valid knowledge about heat exchangers. The article also deals with the determination of the limit values defining the values range of these key variables.

Design and finite volume evaluation of a counterflow recuperative spiral heat exchanger for additive manufacturing

“…In this case helium or hydrogen was used as working fluid for the Stirling engine with small dimeter tubes in the range of 3.0mm to 6.0mm constructed as part of the heat exchanger. Two incoming and two outgoing streams describe the stationary operation of any recuperative heat exchangers [14]. The various calculation methods for recuperative heat exchangers with two incoming and two outgoing streams include LMTD and NTU [15].…”

HVAC Systems Heat Recovery with Multi-Layered Oscillating Heat Pipes

“…Another necessary value used during every recuperative heat exchanger design calculation is represented by a logarithmic mean temperature difference correction factor (ε ∆ ̅ ). For any combination of 1 and 1 values calculated from the experimentally measured data in this article the value of ε ∆ ̅ is approximately equal to 1(ε ∆ ̅ ≈ 1) [20]. When the value of logarithmic mean temperature difference correction factor was obtained, the number of transfer units 1 was calculated.…”

“…In general, recuperative heat exchangers are commonly described by the values of heat capacity rate ratio ( ), dimensionless temperature change ( ) and number of transfer units ( ). The values of , and are related to a so-called weak stream (the stream with the lower value of a heat capacity) [19,20] commonly indicated by subscript 1. Based on the experimental data, the values of the dimensionless temperature change 1 and heat capacity rate ratio 1 ranged as follow: 1 ∈ 〈0.141; 0.176〉 and 1 ∈ 〈0.826; 0.959〉.…”

Suitability Assessment of Two Types of Heat Exchangers for High Temperature, Naturally Circulating Helium Cooling Loop

“…For this reason, the research of helium cooling loop systems is very topical. The research activities in the given area from several aspects are documented in the various publications, as for example [1,2,3,4,5,6,7,8,9,10].…”