Janybek Orozaliev[3] [4]*, Christian Budig1, Klaus Vajen1, Elimar Frank1#,
Ruslan Botpaev[5], Alaibek Obozov2

1 Kassel University, Institute of Thermal Energy Engineering, Kassel (Germany)

2 Kyrgyz State Technical University, Department for Renewable Energies, Bishkek (Kyrgyzstan)
Corresponding Author, www. solar. uni-kassel. de

Abstract

A fin-and-tube heat exchanger model is presented in this paper. It uses empirical heat transfer and flow friction correlations identified in the literature. The model structure, its range of validity and accuracy are described in detail. Additionally, the model performance is compared with the producer design software GPC.

1. Introduction

Fin-and-tube heat exchangers are widely used in industry and residential air conditioning for heat transfer between a liquid and a gas, e. g. for water cooling, air cooling or heating. In the context of a research project in Bishkek (Kyrgyzstan) such a heat exchanger is applied in a multicomponent solar thermal system [1] to heat up cold water for a district heating net by using the enthalpy of the ambient air. The ambient air is also preheated with an unglazed transpired air collector before going through a heat exchanger.

In practice, the heat exchanger geometry is selected by designers relying on their personal experience and some recommendations1. If the heat capacity rate ratio of liquid to air is not defined by the application, a typical value (e. g. 2) is applied. This procedure works well for standard applications. But for non-standard applications with different boundary conditions (e. g. low electricity prices) as described above, there are more detailed investigations necessary. In order to optimize the heat exchanger configuration for this application, a detailed heat exchanger model was developed, which is presented in this paper.