Process gains

Activity tab in model data

Set the thermal gains due to process heat per unit floor area.  

Gain

Set the design level of energy consumption due to process activity per unit floor area. Process heat is the heat from any manufacturing or industrial process which is part of the business activity. The actual heat gain to the space may be reduced through the Fraction lost data (below).

The Gain, entered in Watts/m2 (or Watts/ft2), is typically used to represent the maximum fuel consumption of process equipment in a zone that is then multiplied by a schedule fraction (below). This is slightly more flexible in that the design level could be a 'diversity factor' applied to a schedule of real numbers. Note that while the schedule value can vary from hour to hour, the design level field is constant.

Tip: Spaces such as industrial units can have very high process gain densities and you may need to Switch off the slider controls from the Program options dialog to enter these high values.

Tip: You can enter negative process gains for modelling the cooling effect from refrigeration units such as those found in supermarkets where the refrigerator doors may open and cool air may enter the zone.Note that Negative process gains are modelled in EnergyPlus using 'Other equipment' data instead of the usual 'Electrical equipment' data. The energy from negative process gains is calculated in the same way as for positive gains.

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 process 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 electrical energy converted to mechanical work or heat that is vented to the atmosphere.

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 process 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 process equipment. This latent energy affects the moisture balance within the zone.

Radiant fraction

This 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 process 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 process 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.

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.