Heat exchangers are a well established tool for the thermal processing of materials, such as cooking, pasteurisation and sterilisation, as well as heating or cooling. When it comes to choosing the right heat exchanger for a particular situation, there is no substitute for professional advice, but you should have a basic understanding of the factors which need to be considered.
1. Is a heat exchanger the right technology?
While heat exchangers are preferable in many situations, they may be over-kill for simple situations where a straightforward heating element or simpler refrigeration system is sufficient.
2. What type of heat exchanger do I need?
The simplest forms of heat exchangers are plate heat exchangers. They are simple and cost effective and can do a very good job with simple Newtonian fluids like milk. However, for more viscous substances, non-Newtonian fluids and processes requiring high levels of heat transfer, tube-in-tube heat exchangers may be a better option.
These come in different forms including corrugated tubes to prevent fouling and improve operating efficiency. For high fouling and viscous fluids, reciprocating or rotary scraped surface heat exchangers are available. These maintain product characteristics while providing maximum operating efficiency.
3. Will the system cope with my products?
The heat exchanger must be capable of providing the right amount of heat transfer. Different materials have different thermal properties and factors such as viscosity, solids content and texture need to be assessed alongside product flow rates to ensure that the product receives the correct treatment.
If the system does not handle certain products correctly it can change or damage their quality. The installation should also be capable of handling the maximum amount of product required.
4. What other benefits could the system deliver?
One of the benefits of many HRS heat exchangers is their ability to recover heat from the end of the process and re-use it. This enables the system to be more efficient, or where the heat source is plentiful – then the recaptured heat can be used for another process or for general heating. These additional cost savings need to be offset against the capital and running costs of the heat exchanger.
5. What are the maintenance requirements?
These will vary according to the type of heat exchanger, its design, and its use. How easy is maintenance? For example, is it possible to remove individual tubes without dismantling the entire unit, and is it possible to service the unit without shutting down the whole process? These factors will have a key impact on how much the heat exchanger costs to service.
6. How much will the system cost?
Cost will be one of the most important factors in making an investment decision. However, it is important to compare both the capital cost and anticipated operating costs and service life. A higher purchase price may be recouped by greater product efficiency and reduced serving costs.
7. How will the system be designed?
Does the company use the very latest scientific information? While it is imperative that the heat exchanger performs correctly in terms of thermal transfer, other considerations, such as ease of installation and maintenance, are important.
8. What back-up and support is there?
Does your supplier offer features such as extended maintenance and servicing? Would you be able to take advantage of any future upgrades, such as improvement in tube design?
It is obviously impossible to cover every potential situation in an article such as this, but I hope that I have highlighted some of the most common issues. Your individual circumstances will be unique and another key consideration when making your final decision should be how well your chosen supplier appreciates this.
By Matt Hale, International Sales Manager, HRS Heat Exchangers
