This work presents an experimental and theoretical evaluation of the thermal performance of a square straight diffusion-bonded stainless steel compact heat exchanger. A one-dimensional steady-state thermal model was proposed to predict the thermal characteristics of the heat exchanger. To validate the model and to study the thermal behavior of the heat exchanger, an experimental test apparatus was developed. The heat exchanger was tested in several combinations of Reynolds ranging from 2600 to 7500, representing transition to turbulent regimes. The temperatures were varied from 70 C to 80 C for the water and from 25 C to 42 C for the air, at the inlet of the heat exchanger, respectively. A good agreement between the experimental data and the analytical model was obtained.

Introduction

In the petroleum and process industries, shell and tube or variations represent about 35% of the total of the heat exchangers used, being by far the most popular technology [1,2]. Although these types of heat exchangers are reliable and robust, their large volumes and footprint area make them not appropriate to be used in some applications [1,3]. On the other hand, compact heat exchangers are highly efficient, as their main characteristic is their large heat transfer surface area for a fixed volume. Although these devices have evolved considerably lately to new efficient solutions, they still deserve a great deal of research around the world. Compact heat exchangers have been developed for applications where requirements of small weight and space are mandatory, as encountered in aerospace, naval and automotive fields. In many heat exchangers especially the compact ones, hot and/or cold streams may flow through non-circular cross-section ducts, i.e., triangular or rectangular, among other geometries. The lengths of these ducts are usually small. The equipment may operate in several regimes, varying from laminar to turbulent. Advanced heat exchangers, like the printed circuit (PCHE), are compact devices characterized by a large heat transfer surface to volume ratio, which presents high effectiveness and low terminal temperature difference. Generally, the compact heat exchanger is fabricated from a large number of plates with channels, chemically etched or water–jet machined [4,5]. After a stacking process, a diffusion bonding technique is applied for fabricating the cores.