Cooling Tower Heat Rejection Calculation

Heat Rejection Formula:

\[ Q = m \times c_p \times (T_{in} - T_{out}) \]

Mass Flow Rate (m):

kg/s

Specific Heat Capacity (c_p):

J/kg·K

Inlet Temperature (T_in):

°C

Outlet Temperature (T_out):

°C

Heat Rejection (Q):

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1. What is Cooling Tower Heat Rejection?

Cooling tower heat rejection refers to the amount of thermal energy removed from a system by the cooling tower. It represents the heat transferred from the process water to the atmosphere through evaporation and sensible heat transfer.

2. How Does the Calculator Work?

The calculator uses the fundamental heat transfer equation:

\[ Q = m \times c_p \times (T_{in} - T_{out}) \]

Where:

\( Q \) — Heat rejection rate (Watts)
\( m \) — Mass flow rate of water (kg/s)
\( c_p \) — Specific heat capacity of water (J/kg·K)
\( T_{in} \) — Inlet water temperature (°C)
\( T_{out} \) — Outlet water temperature (°C)

Explanation: This equation calculates the thermal energy removed based on the water flow rate and temperature difference across the cooling tower.

3. Importance of Heat Rejection Calculation

Details: Accurate heat rejection calculation is essential for proper cooling tower sizing, energy efficiency analysis, system performance evaluation, and maintenance planning in HVAC and industrial processes.

4. Using the Calculator

Tips: Enter mass flow rate in kg/s, specific heat capacity in J/kg·K (4186 for water), and temperature values in °C. All values must be valid (mass flow > 0, specific heat > 0).

5. Frequently Asked Questions (FAQ)

Q1: What is the typical specific heat capacity for water?
A: The specific heat capacity of water is approximately 4186 J/kg·K at standard conditions.

Q2: How do I convert flow rate from m³/h to kg/s?
A: Multiply m³/h by 1000 (density of water in kg/m³) and divide by 3600 (seconds in hour): kg/s = (m³/h × 1000) ÷ 3600.

Q3: What are typical temperature ranges for cooling towers?
A: Typical approach temperatures range from 2-8°C, with cooling ranges typically between 5-15°C depending on design.

Q4: Why is heat rejection important in cooling tower selection?
A: Proper heat rejection calculation ensures the cooling tower can handle the thermal load, preventing system inefficiency and equipment failure.

Q5: How does ambient conditions affect heat rejection?
A: Wet-bulb temperature, relative humidity, and air flow significantly impact cooling tower performance and actual heat rejection capacity.