Novel Heat Exchanger Design Choices for High Temperature Gas Applications

Introduction

Several businesses demand heat exchange between gases or liquids, when both gases and liquids are corrosive and, in some cases, at high temperatures. They can be found in fuel cells, gas heating, waste energy recovery, and other applications.

In most of those applications, the temperature on the hot side is in the 600° to 900° C region, whereas the cold side is a gas or liquid. The gases become highly corrosive at those high temperatures, and we may end up with a serious corrosion problem in our process. Furthermore, several of the applications begin with a corrosive liquid, such as deionized water, distilled water, KOH, and others.

Owing to the aforementioned difficulties, the thermal and mechanical design of a robust and effective gas-to-liquid heat exchanger is a significant task.

Solutions That Are Currently Available

There are various types of heat exchangers that can deal with high temperatures, corrosiveness, and varying work pressure.

BPHE - Brazed Plate Heat Exchanger.

This type of heat exchanger can handle high temperatures and corrosiveness. Yet, there are some drawbacks to adopting BPHE:

Special materials for the plates, as well as brazing materials, are required.

While utilizing the BPHE, there is a problem with pressure decrease. To accomplish the desired tiny pressure drop, we must plan on using numerous BPHEs in tandem, which raises the volume and consequently the expense of the BPHE.

When the temperature rises, the allowed operating pressure for BPHE decreases. At 750° C, no pressure more than 2 Bars can be used.

Heat Exchangers with Shell and Tube

Straight tubes or U-shaped tubes are the two possibilities for shell and tube heat exchangers. When working with high temperatures and corrosive materials, the shell and tube heat exchanger can obtain the needed results. They have an advantage over the BPHE in terms of working under high pressure, but they still have numerous disadvantages:

Because the thermal efficacy is lower, a bigger heat transfer surface is required, which increases the volume of the heat exchanger and hence the cost of one.

The manufacturing process involves several welds, which may cause dependability issues over time.

Heat Exchangers with Fins and Tubes

We can now design and build fin and tube heat exchangers for high-temperature, corrosive liquids and gases. Furthermore, they can be used for high working pressure applications, both gas and liquid (up to 550 Bars).

When compared to both BPHE and shell and tube heat exchangers, fin and tube heat exchangers have numerous advantages:

The fin and tube heat exchanger can withstand working pressures of up to 550 Bars.

The fin and tube heat exchanger may reach 0.1 Pascal pressure drop.

Many varieties of stainless steel can be used to make the fin and tube heat exchanger (both fin and tubes). 316, 310, Inconel, SMO, Duplex, and other alloys are examples. As a result, we can tailor the material to the appropriate temperature and corrosiveness of the gas or liquid.

The heat exchange surface area is higher when using fin and tube heat exchangers, providing a very good thermal solution.

The fin and tube heat exchanger transfers heat in corrosive environments and at temperatures up to 1250° C.

The mechanical procedure of attaching the fin to the tube ensures greater longevity and reliability.

The production procedure for the fin and tube heat exchanger is less expensive than for the other heat exchangers described, allowing for a highly reasonable price.

Designing the heat exchanger based on customer size requirements is relatively simple and inexpensive.

The inability to produce a thermal design was formerly one of the impediments to adopting the fin and tube heat exchanger for these types of industrial applications. This barrier has been removed as a result of recent improvements, and we can now provide thermal and mechanical design for the majority of operating conditions (corrosiveness, high temperature, and pressure).

Summary

The challenge of designing and manufacturing heat exchangers for applications involving corrosive gases or corrosive liquids at high temperatures is becoming more significant as energy prices rise and demand for green energy such as fuel cells, natural gas usage, waste energy recovery, and others grows.

Utilizing fin and tube technology in conjunction with various types of stainless steel allows us to deliver heat exchange at practically any temperature and for the majority of corrosive liquids and gases while remaining effective and reliable.

Vrcoolertech specializes in the design and fabrication of specialized heat exchangers for the following industries: fuel cells, gas applications, waste energy recovery, high temperatures, and corrosive gases and liquids.

Please do not hesitate to contact us if you have any queries or concerns.