Calculate air-to-water heat exchanger heat transfer, temperature rise, and LMTD sizing to solve for Q, U, or area from end temperatures.

Sensible heat for one fluid stream: Q = mass flow ร— specific heat ร— temperature change. Use outlet minus inlet temperature; negative Q means heat removed. No phase change or latent heat.

Numeric examples: 4181.3, 1006, 3690 J/(kgยทK). Verify the value for your fluid, composition and temperature; these are not certified material data.

Outlet minus inlet; this is a difference, not an absolute temperature.

Related Calculators

Air To Water Heat Exchanger Formula

For a single fluid stream without phase change, the following sensible-energy balance uses constant specific heat and signed outlet-minus-inlet temperature change. Choose the quantity under Solve for, enter the displayed inputs, then select Calculate.

Q = m ร— c ร— Delta T

Variables:

  • Q is the heat transfer rate in watts
  • m is the mass flow rate in kilograms per second (kg/s)
  • c is the specific heat capacity in joules per kilogram per degree Celsius (J/(kgยทK))
  • ฮ”T is the temperature change in degrees Celsius (ยฐC)

To calculate the heat transfer rate, multiply the mass flow rate by the specific heat capacity and the temperature change. Negative heat rate means heat removed from that stream. LMTD modes instead use positive duty: Q = U ร— A ร— LMTD, for ideal counterflow or parallel flow. Both terminal hot-minus-cold differences must be positive; equal positive differences give that same LMTD. Crossflow and multipass corrections are not included. Use U and A on the same surface-area basis.

Watts to BTU/hr Conversion Table (Heat Transfer Rate, Q)
Watts (W) BTU/hr
100341
200682
3001024
4001365
5001706
6002047
7502559
1,0003,412
1,2004,095
1,5005,118
2,0006,824
2,5008,530
3,00010,236
3,50011,942
4,00013,649
5,00017,061
7,50025,591
10,00034,121
20,00068,243
50,000170,607
1 W โ‰ˆ 3.412142 BTU/hr โ€ข 1 BTU/hr โ‰ˆ 0.293071 W

What is an Air To Water Heat Exchanger?

An air to water heat exchanger is a device that transfers heat from air to water. It is commonly used in heating, ventilation, and air conditioning (HVAC) systems to improve energy efficiency and maintain desired temperatures. The heat exchanger works by passing air over a series of coils or plates that contain water. As the air flows over the coils, heat is transferred from the air to the water, thereby cooling the air and heating the water. This process can be reversed to transfer heat from water to air, depending on the application.

How to Calculate Air To Water Heat Exchanger?

The following steps outline how to calculate the heat transfer rate for an air to water heat exchanger.

  1. First, select Sensible heat: heat rate and determine the mass flow rate (m) in kg/s.
  2. Next, determine the specific heat capacity (c) in J/(kgยทK).
  3. Next, determine the outlet-minus-inlet temperature change (ฮ”T) in ยฐC.
  4. Finally, calculate the heat transfer rate (Q) using the formula Q = m * c * ฮ”T.
  5. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Mass flow rate (m) = 2 kg/s

Specific heat capacity (c) = 4186 J/(kgยทK)

Temperature change (ฮ”T) = 10 ยฐC; Q = 2 ร— 4186 ร— 10 = 83,720 W.