The formula to calculate the Cooling Degree Hours (CDH) is:
\[ CDH = (T - T_b) \times t \]
Where:
Cooling degree hours (CDH) are a measure used in the field of meteorology and HVAC (heating, ventilation, and air conditioning) to quantify the demand for energy needed to cool a building. CDH is calculated by taking the difference between the outdoor temperature and a base temperature (usually 18°C or 65°F) and multiplying it by the number of hours the temperature remains above the base temperature. This metric helps in understanding the cooling requirements and energy consumption for air conditioning systems over a specific period.
Let's say the temperature (T) is 25°C, the base temperature (Tb) is 18°C, and the time (t) is 5 hours. Using the formula:
\[ CDH = (25 - 18) \times 5 = 35 \]
So, the cooling degree hours (CDH) is 35.
Definition: Cooling degree days (CDD) measure how much (in degrees) and for how long (in days) the outside temperature was above a certain base temperature.
Formula: \( \text{CDD} = \sum (T_{\text{avg}} - T_{\text{base}}) \)
Example: \( \text{CDD} = (25 , \text{°C} - 18 , \text{°C}) + (27 , \text{°C} - 18 , \text{°C}) \)
Definition: The formula for calculating cooling degree days.
Formula: \( \text{CDD} = \sum (T_{\text{avg}} - T_{\text{base}}) \)
Example: \( \text{CDD} = (30 , \text{°C} - 18 , \text{°C}) + (28 , \text{°C} - 18 , \text{°C}) \)
Definition: The rate of cooling is the change in temperature over time.
Formula: \( \frac{\Delta T}{\Delta t} \)
Example: \( \frac{20 , \text{°C} - 15 , \text{°C}}{2 , \text{hours}} \)
Definition: These calculations determine the heating or cooling load required to maintain a desired temperature.
Formula: \( Q = mc\Delta T \)
Example: \( Q = 5 , \text{kg} \times 4.18 , \text{kJ/kg°C} \times (25 , \text{°C} - 20 , \text{°C}) \)
Definition: Heating degree days (HDD) measure how much (in degrees) and for how long (in days) the outside temperature was below a certain base temperature.
Formula: \( \text{HDD} = \sum (T_{\text{base}} - T_{\text{avg}}) \)
Example: \( \text{HDD} = (18 , \text{°C} - 10 , \text{°C}) + (18 , \text{°C} - 12 , \text{°C}) \)
