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How to Test a Heat Exchanger's Performance

A heat exchanger is a piece of chemical process equipment that uses the difference in temperatures of two separate fluid streams. The most common heat exchanger design is the shell and tube. This configuration has one fluid flowing through a block of parallel tubes and a second fluid flowing countercurrently around the outside of the tubes. The performance of a heat exchanger is measured by comparing the design temperature differences and flow rates with actual measurements. The actual measurement is divided by the design for an efficiency value.

Things You'll Need

Pen
Paper
Calculator

Instructions

- 1
  Determine the design conditions of a shell and tube heat exchanger. For instance, assume cold water is entering the tubes at 40 degrees F. The design calls to heat the water to 75 degrees F using steam on the shell side of the exchanger. The flow rate of the cold water is 100 gallons per minute and the steam is measured at 2,000 pounds per hour (steam is measured in mass flow rates). Therefore, the temperature difference of the cold water is designed to be 35 degrees.
- 2
  Determine the actual flow conditions, inlet and outlet temperatures of the cold water. In practice, this is done by the installation of local pressure, flow rate and temperature measuring instruments. At any given time, operators can determine the conditions surrounding the heat exchanger. Assume the water inlet is measured at 40 degrees F and the outlet temperature is 68 degrees F. This is an actual temperature difference of 28 degrees.
- 3
  Calculate the efficiency of the heat exchanger by dividing the actual temperature difference by the design and multiplying by 100 to get a percentage. This is 28 / 35 x 100, or 80%. To increase this performance value, you would decrease the water flow rate or increase the steam flow rate.

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