How to Select and Size a Heat Exchanger

May 27, 2020

Heat exchangers are used throughout industrial processes whenever heat needs to be transferred from one medium to another. Understanding how to size and select a heat exchanger benefits both productivity and the bottom line. The Carotek Heat Exchanger Selection Guide provides a model of the heat exchanger sizing and selection process.

Types of Heat Exchangers

By its most basic definition, an industrial heat exchanger transfers thermal energy from one fluid to another without mixing them. Heat exchangers can be generally classified into a few main types:

Shell and Tube heat exchangers consist of a shell enclosing a number of tubes. Because they are widely used, these versatile heat exchangers are generally well understood. The shell and tube design helps these heat exchangers withstand a wide range of pressures and temperatures.

Plate and Frame heat exchangers are compact, efficient products designed with a number of stacked heat transfer plates clamped together within a frame.

Gasketed Plate heat exchangers feature titanium or other nickel alloys for accurate fluid temperature control for heat recovery. These designs are often used for food or sanitary applications.

Brazed Plate heat exchangers are constructed without gaskets, and they are suited for greater range of pressures and temperatures. Available in materials like copper or nickel, these corrosion resistant heat exchangers are suitable for many applications.

For any given application, there is usually more than one heat exchanger design that could be used. A starting point for heat transfer solution sizing and selection is to compare models that fit the temperatures and pressures required for the process. The best type of heat exchanger depends on design parameters, fluid characteristics, space, and budget.

Main Criteria for Heat Exchanger Sizing and Selection

  • Function that the heat exchanger will perform (whether condensing, boiling, etc.)
  • Pressure limits (high/low), which may vary throughout the process, and pressure drops across the exchanger
  • Approach temperature and temperature ranges (which may vary throughout the process)
  • Fluid flow capacity
  • Materials requirements. Conditions like sudden temperature changes or corrosive media may require special materials. For a gasketed plate heat exchanger, the gaskets must be compatible with the fluids in the unit.
  • Thermal fluid characteristics and product mix. If the heating or cooling fluid is susceptible to fouling, a corrosion resistant material may be needed.
  • Location. Some exchangers may require cooling water, steam, or hot oil, and they may be relevant options only where these utilities are available.
  • Footprint. Space limitations and layout may also affect which heat exchanger models are suitable. Keep in mind that lower approach temperatures generally correlate to larger units.
  • Maintenance requirements. Depending on housekeeping procedures, it may be useful to choose a design lends itself to easy cleaning. Ease of repair or inspection may be a factor as well.

Generally, more than one heat exchanger model will work for a given application, so additional criteria may help in evaluating the best fit. Consider factors like future scalability, overall cost to purchase and operate, and efficiency/carbon footprint to narrow the options.

Importance of Sizing a Heat Exchanger

Once a heat exchanger design is selected, the most efficient size depends on operating conditions. For example, if operating temperatures vary seasonally, both the winter and summer cooling (or heating) load must be calculated. The most efficient plate exchanger model is the smallest model with the same plate corrugation that is capable of handling the flow in both seasons.

Thermodynamic equations can help arrive at the best solution, where flow, temperature, and pressure drop are all within acceptable limits. Due to the number of dependent variables in heat transfer solution sizing and selection, complex equations are often used for selecting the optimal solution. Heat exchangers can often be tailored, and specifications like the size and number of plates are often customized for the application.

Carotek is an authorized distributor of Standard Xchange heat exchangers, and Carotek engineers are specially trained to assist with finding the optimal heat exchanger to meet your specifications. The following data sheet can be used to provide the requirements for your heat transfer solution.

Data Required for Selection of a Standard Xchange Heat Exchanger

The image below details all of the data necessary for proper sizing.  Download this guide for a fill-in version.

Heat exchanger sizing and selection requires a combination of knowledge of the heat exchanger types and options as well as knowledge of the application and environment where the unit operates. 

 Contact Carotek to review your needs and heat exchanger options.

Or browse our selection of heat exchangers to find the best fit for your application.