General model description.

Building Design and Use

Architecture

The building is a single room based on the BESTEST Case 900 model definition. The floor dimensions are 6m x 8m and the floor-to-ceiling height is 2.7m. There are four exterior walls facing the cardinal directions and a flat roof. The walls facing east-west have the short dimension. The south wall contains two windows, each 3m wide and 2m tall. The use of the building is assumed to be a two-person office with a light load density.

Constructions

The constructions are based on the BESTEST Case 900 model definition. The exterior walls are made of concrete block and insulation, while the floor is a concrete slab. The roof is made of wood frame with insulation. The layer-by-layer specifications are (Outside to Inside):

Exterior Walls
Name Thickness [m] Thermal Conductivity [W/m-K] Specific Heat Capacity [J/kg-K] Density [kg/m3]
Layer 1 0.009 0.140 900 530
Layer 2 0.0615 0.040 1400 10
Layer 3 0.100 0.510 1000 1400
Name IR Emissivity [-] Solar Emissivity [-]
Outside 0.9 0.6
Inside 0.9 0.6

Floor
Name Thickness [m] Thermal Conductivity [W/m-K] Specific Heat Capacity [J/kg-K] Density [kg/m3]
Layer 1 1.007 0.040 0 0
Layer 2 0.080 1.130 1000 1400
Name IR Emissivity [-] Solar Emissivity [-]
Outside 0.9 0.6
Inside 0.9 0.6

Roof
Name Thickness [m] Thermal Conductivity [W/m-K] Specific Heat Capacity [J/kg-K] Density [kg/m3]
Layer 1 0.019 0.140 900 530
Layer 2 0.1118 0.040 840 12
Layer 3 0.010 0.160 840 950
Name IR Emissivity [-] Solar Emissivity [-]
Outside 0.9 0.6
Inside 0.9 0.6

The windows are double pane clear 3.175mm glass with 13mm air gap.

Occupancy schedules

There is maximum occupancy (two people) from 8am to 6pm each day, and no occupancy during all other times.

Internal loads and schedules

The internal heat gains from plug loads come mainly from computers and monitors. The internal heat gains from lighting come from hanging fluorescent fixtures. Both types of loads are at maximum during occupied periods and 0.1 maximum during all other times. The occupied heating and cooling temperature setpoints are 21 C and 24 C respectively, while the unoccupied heating and cooling temperature setpoints are 15 C and 30 C respectively.

Climate data

The climate is assumed to be near Denver, CO, USA with a latitude and longitude of 39.76,-104.86. The climate data comes from the Denver-Stapleton,CO,USA,TMY.

HVAC System Design

Primary and secondary system designs

Heating and cooling is provided to the office using an idealized four-pipe fan coil unit (FCU), presented in Figure 1 below. The FCU contains a fan, cooling coil, heating coil, and filter. The fan draws room air into the unit, blows it over the coils and through the filter, and supplies the conditioned air back to the room. There is a variable speed drive serving the fan motor. The cooling coil is served by chilled water produced by a chiller and the heating coil is served by hot water produced by a gas boiler.


Figure 1: System schematic.


Equipment specifications and performance maps

For the fan, the design airflow rate is 0.55 kg/s and design pressure rise is 185 Pa. The fan and motor efficiencies are both constant at 0.7. The heat from the motor is added to the air stream. The COP of the chiller is assumed constant at 3.0. The efficiency of the gas boiler is assumed constant at 0.9.

Rule-based or local-loop controllers (if included)

A baseline thermostat controller provides heating and cooling as necessary to the room by modulating the supply air temperature and fan speed. The thermostat, designated as C1 in Figure 1 and shown in Figure 2 below, uses two different PI controllers for heating and cooling, each taking the respective zone temperature set point and zone temperature measurement as inputs. The outputs are used to control supply air temperature set point and fan speed according to the map shown in Figure 3 below. The supply air temperature is exactly met by the coils using an ideal controller depicted as C2 in Figure 1. For heating, the maximum supply air temperature is 40 C and the minimum is the zone occupied heating temperature setpoint. For cooling, the minimum supply air temperature is 12 C and the maximum is the zone occupied cooling temperature setpoint.


Figure 2: Controller C1.


Figure 3: Mapping of PI output to supply air temperature set point and fan speed in controller C1.


Model IO's

Inputs

The model inputs are:

Outputs

The model outputs are:

Forecasts

The model forecasts are: