Issues discussed below will provide you with a good starting point to begin a tender process or a basis to compare proposals.
1.Is a heat exchanger right for me?
The first question you should ask is whether you need one in the first place. There is no doubt that heat exchangers can be relatively complex and expensive. While they are preferable in many situations, particularly where a cooling or heating source is already available or is required for more than one process, they may be over-kill for simple situations where a straightforward heating element or simpler refrigeration system is enough.
2. What type do I need?
The simplest forms of heat exchangers are so-called plate heat exchangers, which consist of combinations of plates and gaskets through which the product and the heating or cooling medium move. They are relatively simple and cost effective and can do a very good job with simple Newtonian fluids like milk and thin oils. However, for more viscous substances, and processes requiring high levels of heat transfer, tube-in-tube heat exchangers may be a better option.
These come in different forms including those with corrugated tubes to increase product turbulence, which prevents fouling and improves operating efficiency. For high fouling and viscous fluids, scraped surface heat exchangers are available. Reciprocating and rotary versions are available, allowing different products to be handled carefully, so that key quality characteristics can be maintained or mixing increased, while providing maximum operating efficiency.
3. Is it compatible with my products?
There are several things to consider. First, the heat exchanger must be capable of providing the right amount of heat transfer. Different materials will have different thermal properties which must be considered when designing a heat exchanger. Factors such as viscosity, solids content and texture will need to be assessed alongside product flow rates to ensure that the product receives the correct treatment. For example, if the heat exchanger does not deliver sufficient heat it may result in an incomplete process, which could have severe implications for product safety.
At the same time, if the system does not handle certain products correctly it can change or damage your products. For example, rough handling of viscous sauces can have a negative effect on their texture.
Finally, the heat exchanger set-up should be capable of handling the maximum amount of product required at any time. While there will be physical constraints on the size of individual heat exchanger elements, in most cases it is possible to combine multiple units in a way to increase treatment capacity.
4. are there other benefits?
One benefit of some heat exchangers is their ability to recover heat from the end of the process and re-use it. In many cases this enables the system to reduce the amount of heat needed to be supplied in the first place. However, in some situations, such as where the heat source is plentiful – then the recaptured heat can be used for another process or for something else altogether, such as heating offices or buildings.
In such cases, 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 chosen, its design, and the environment in which it is used. However, more important than the actual maintenance requirements is how easy upkeep is. For example, how hard is it to access key components and what are the costs of spare parts such as seals and gaskets?
For double- and triple-tube heat exchangers, is it possible to remove individual tubes without dismantling the entire unit, and is it possible to service parts 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 this cost?
Though cost is one of the most important factors in making a decision, it is important to compare both the capital cost of different units and their anticipated operating costs and service life. For example, a 25 per cent higher purchase price may easily be recouped by greater operating efficiency and reduced serving costs over the same, or even longer, working life. By considering all associated costs will you be able to make an accurate investment decision.
7. How is the system designed?
Does the supplying company use the very latest scientific information on energy and heat transfer, or is it relying on papers and data which may be years old? 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 also important.
8. What back-up and support is there?
A back-up plan in the event of a problem is important, but does your supplier offer features like extended maintenance and servicing? Would you be able to take advantage of future upgrades, such as improvement in tube design? It may not be essential to deal with a company which is based locally, but you should investigate how well they deal with other clients in similar circumstances.
It is obviously impossible to cover every potential situation in an article such as this, but this article highlights some of the most common issues that apply to nearly every heat exchanger purchase or installation. Your individual circumstances will be unique and another key consideration when making your final decision should be how well your chosen supplier appreciates this.
Matt Hale is the International Sales & Marketing Director of HRS Heat Exchangers
Heat exchangers for your bakery
What are they and are they right for you? |
When it comes to choosing the right heat exchanger, there is no substitute for professional advice, but you will have a better handle on the process if you understand which factors to consider. These can be divided into commercial considerations and technical considerations.
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