Compare Energy Use in Variable Refrigerant Flow Heat Pumps Field Demonstration and Computer Model Page: 2 of 9
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model for increased accuracy. The results of the comparison of simulation outputs and measured data are discussed.
The specifications of the installed VRF system are shown in Table 1. The table contains system parameters as
obtained from the manufacturer's catalog data and also as measured in the lab. Measured system parameters are shown in
parenthesis. For the simulation study of the installed VRF system, lab measured parameters are used.
Table 1. VRF Heat Pump System Specification at EPRI Test Facility
System Parameter Description
Nominal Cooling Capacity 21.1 (18.47) kW [72 (63) kBTU/hr]
Nominal Cooling Power Input 5.55 (6.71) kW [18.9 (22.9) kBTU/hr]
Cooling COP 3.8 (2.75) W/W [13 (9.4) BTU/W-hr]
Nominal Heating Capacity 23.4 (25.39) kW [79.8 (86.6) kBTU/hr]
Nominal Heating Power Input 6.04 (6.47) kW [20.6 (22) kBTU/hr]
Heating COP 3.87 (3.92) W/W [13.2 (13.4) BTU/W-hr]
Minimum Outdoor Temperature in Cooling Mode -5 0C [23 0F]
Maximum Outdoor Temperature in Cooling Mode 43 0C [109.4 0F]
Minimum Outdoor Temperature in Heating Mode -21 0C [-5.8 0F]
Maximum Outdoor Temperature in Heating Mode 35 0C [95 0F]
Terminal Unit Rated Total Cooling Capacity 6000.00 W [20.47 kBTU/hr]
Terminal Unit cooling SHR 0.79866
Terminal Unit Rated Total Heating Capacity 6782.00 W [23.13 kBTU/hr]
Terminal Unit Rated Air Flow rate (Cooling/Heating) 0.333 (m3/s) [705 CFM]
BUILDING AND TEST CONDITIONS
Geometry of the building is shown in Figure 1 below. The building consists of office space, workout room, cubicles,
lab and warehouse. VRF system indoor units are installed in the lab and warehouse part of the building. The remaining
portions of the buildings were conditioned by separate HVAC systems. The lab is divided into zones 1 and 2 based on
terminal units 1 and 2 and warehouse is divided into zones 3 and 4 based on terminal unit 3 and 4. Zones 1 through 4 are
separated by the remaining space of the building through adiabatic walls.
The thermo-physical properties of the construction materials of the building are shown in Table-2 below.
Table 2. Thermo-Physical Properties of the Construction Material of the Building
Thickness(m) Conductivity Density Specificheat(J/kg.K)
Layers (outer to inner) [ft] (W/m.K) (kg/m3) [BTU/lb/F]
Roof membrane 0.0095[0.031] 0.0016 [0.0009] 1121.29  1460.00 [0.35]
Metal decking 0.0015[0.005] 45.006  7680.00 418.40 [0.1]
Roof indulation 0.30 [0.984] 0.090 [0.05] 265.00 [16.5] 836.80 [0.2]
Filled concrete blocks #1 0.079 [0.26] 1.378 [0.8] 1731.45 838 [0.2]
Filled concrete blocks #2 0.127 [0.42] 1.065 [0.615] 1031.57  419 [0.1]
Filled concrete blocks #3 0.089 [0.29] 1.437 [0.83] 1647.86 838 [0.2]
High weight concrete 0.1016 [0.33] 1.31 [0.75] 2243.0  837.0 [0.2]
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Sharma, Chandan & Raustad, Richard. Compare Energy Use in Variable Refrigerant Flow Heat Pumps Field Demonstration and Computer Model, article, June 1, 2013; United States. (digital.library.unt.edu/ark:/67531/metadc831612/m1/2/: accessed January 16, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.