Calculating Airflow Rates and Cooling Loads in Commercial Kitchens

Vocabulary practice flashcards covering airflow rate, enthalpy calculations, moisture loads, and cooling load determination in commercial kitchens.

Total Heat Gains ($Q_{tot}$)

The total thermal load in a kitchen in kW, calculated as $Q_{tot} = Q_1 + Q_2 + Q_3 + Q_4 + Q_5$, representing the sum of heat gains from kitchen appliances ($Q_1$), people ($Q_2$), electrical lighting ($Q_3$), solar heat through windows and walls ($Q_4$), and outdoor air ($Q_5$).

Simultaneous Coefficient ($K_{SIM}$)

A reduction factor defined as the quotient of the number of appliances in use and the total number of appliances, used to scale heat gains from cooking appliances during peak load estimation.

Total Moisture Emission ($W$)

The total moisture generation in a kitchen in $\text{kg/h}$, calculated as $W = W_1 + W_2 + W_3$, where $W_1$ is moisture from people, $W_2$ is moisture from unhooded kitchen appliances, and $W_3$ is moisture from outdoor air.

Exhaust Mass Flow Rate ($M_{ex}$)

The total exhaust air mass flow rate in $\text{kg/h}$, determined by $M_{ex} = \sum(L_{oi}\rho_i) + L_{gv}\rho_{gv}$, summing the airflow from individual exhaust hoods or ventilated ceilings and the general exhaust ventilation from the upper zone.

Commercial Kitchen Air Balance Rule

The design requirement specifying that the total airflow exhausted from a kitchen must be at least $10\%$ higher than the airflow supplied directly to the kitchen.

Adjacent Spaces Mass Flow Rate ($M_{ad}$)

The mass flow rate of transfer air drawn into the kitchen from adjacent spaces in $\text{kg/h}$, defined as $M_{ad} = L_{ad}\rho_{ad}$, where $L_{ad}$ is the volume airflow rate and $\rho_{ad}$ is the air density.

Supply Mass Flow Rate ($M_{sup}$)

The mass flow rate of air mechanically supplied to the kitchen in $\text{kg/h}$, calculated from the air-balance equation as $M_{sup} = M_{ex} - M_{ad}$.

Process Line ($\varepsilon$)

The ratio representing the path of air state change in $\text{kJ/kg}$, defined as the quotient of total heat gains and total moisture emission: $\varepsilon = \frac{3600 Q_{tot}}{W}$.

Typical Process Line ($\varepsilon$) Range

The typical value range of $\varepsilon$ during maximum kitchen equipment operation, spanning from $5000\,\text{kJ/kg}$ to $7000\,\text{kJ/kg}$ ($2150\,\text{Btu/lb}$ to $3009\,\text{Btu/lb}$) depending on the catering enterprise type.

Occupied Zone Enthalpy ($h_{oz}$)

The enthalpy of air within the occupied zone of the kitchen in $\text{kJ/kg}$, derived from the energy balance equation: $h_{oz} = \frac{3600 Q_{tot} + M_{sup} h_{sup} + M_{ad} h_{ad}}{M_{ex}}$.

Mixture Enthalpy ($h_{mix}$)

The enthalpy of the mixture of supply air and air entering from adjacent spaces in $\text{kJ/kg}$, defined as $h_{mix} = \frac{M_{sup} h_{sup} + M_{ad} h_{ad}}{M_{ex}}$.

Supply Air Temperature Offset

The standard design parameter setting the supply air temperature typically $3^\circ\text{C}$ to $5^\circ\text{C}$ ($5^\circ\text{F}$ to $9^\circ\text{F}$) below the target indoor room air temperature.

Mollier Chart (Kitchen HVAC Application)

The psychrometric diagram utilized to find the supply air enthalpy ($h_{sup}$) and plot the process line ($\varepsilon$) to locate final indoor air parameters at the intersection with the calculated indoor enthalpy.

Hospital and Cafeteria Simultaneous Coefficient

The recommended simultaneous coefficient ($K_{SIM}$) range of $0.5$ to $0.7$ used for hospital and cafeteria kitchens.

Hotel, School, Restaurant, and Industrial Simultaneous Coefficient

The recommended simultaneous coefficient ($K_{SIM}$) range of $0.6$ to $0.8$ applied to hotel, school, restaurant, and industrial kitchens.