Catering gains

Activity tab in model data

Check the Catering > On checkbox to include any cooking gains and other catering activities in the simulation.

Units

When the Gain definition level model option is set to 2-Zone by zone in model data you can select the units to be used for internal gains here on the Activity tab. Choose from the options:

• 1-Power density where zone equipment gains are entered as a power density, i.e. as a power per zone floor area in W/m2 or W/ft2. This option is usually the most convenient method for most general purpose modelling as the data is normalised by area and so can be inherited from levels above in the model hierarchy and can be effectively loaded from Activity template.
• 2-Absolute zone power where zone equipment gains are entered as a power value in W. This option is usually used when detailed zone by zone survey or design data is available. Unless you need to enter specific known lighting equipment gains zone by zone, this option is best avoided as it increases the amount of work involved due to the inheritance mechanism not working effectively for gains that are not normalised by floor area.

Gain

Set the design level of energy consumption due to catering equipment. The actual heat gain to the space may be reduced through the Fraction lost data (below).

Depending on the Equipment gain units model option setting, the gains data is entered either as Absolute zone power in W or as Power density in W/m2 or W/ft2.

Schedule

Select the schedule that governs the timing of gains in the zone. The level of gains are multiplied by the time-varying factor in this schedule to give the gain for each timestep in the simulation.

Fuel

The fuel can be selected from a drop down list. Note that these fuels are currently mapped to a shorter list in the results as follows:

Fraction lost

This field is a decimal number between 0.0 and 1.0 and is used to characterise the amount of 'lost' heat being given off by the catering equipment in a zone. The number specified in this field will be multiplied by the total energy consumed by equipment to give the amount of heat which is 'lost' and does not impact the zone energy balances. This might correspond to cooker heat that is vented to the atmosphere through an extract hood.

Latent fraction

This field is a decimal number between 0.0 and 1.0 and is used to characterize the amount of latent heat given off by catering equipment in a zone. The number specified in this field will be multiplied by the total energy consumed to give the amount of latent energy produced by the catering equipment. This latent energy affects the moisture balance within the zone.

Radiant fraction

This field is a decimal number between 0.0 and 1.0 and is used to characterise the amount of long-wave radiant heat being given off by catering equipment in a zone. The radiant fraction will be multiplied by the total energy consumed by electric equipment and (1-Fraction lost) to give the amount of long wavelength radiation gain from catering equipment in a zone. A value of zero means that the heat gain is entirely convective in which case all the heat is transferred to the air node in simulations.  A value of 1 means that the gain is entirely radiative in which case all the heat is distributed to the inside surfaces. a typical value is somewhere between 0.1 and 0.5.

If the Internal gains operate with occupancy model option is not selected you can also set the operation schedule.

CO2 generation rate

This numeric input field, available only when the fuel is selected as 2-Natural gas, specifies carbon dioxide generation rate with units of m3/s-W or (ft3/min)/(Btu/hr). The default value of 0.0 assumes the equipment is fully vented to outdoors.

In the absence of better information, a value of 3.45E-8 m3/s-W can be used which assumes the equipment is not vented to outdoors. This value is converted from natural gas CO2 emission rate at 11.7 lbs CO2 per therm, the CO2 emission rate provided by U.S. Energy Information Administration. The maximum value for this input field is 3.45E-7 m3/s-W.

Calculation

The fuel input to the equipment ultimately appears as heat that contributes to zone loads. In the simulation this heat is divided into four different fractions. Three of these are given by the input fields Latent fraction, Radiant fraction and Fraction lost. The convected fraction, defined as the fraction of the heat from electric equipment convected to the zone air, is calculated by the program as:

Fconvected = 1.0 – (Latent fraction + Radiant fraction + Fraction lost)

You will get an error message if Fraction Latent + Fraction Radiant + Fraction Lost exceeds 1.0.