# ISO 11855-4:2012 pdf download – Building environment design – Design,dimensioning, installation and control ofembedded radiant heating and coolingsystems — Part 4: Dimensioning and calculation of thedynamic heating and cooling capacity of Thermo Active Building Systems (TABS)

ISO 11855-4:2012 pdf download – Building environment design – Design,dimensioning, installation and control ofembedded radiant heating and coolingsystems — Part 4: Dimensioning and calculation of thedynamic heating and cooling capacity of Thermo Active Building Systems (TABS).

Under the above-mentioned conditions, a cooling load calculation or a simulation for a convective system can be carried out for an entire 24 Ii period and with an internal temperature equal to the average room operative temperature during the occupancy hours. The results of this calculation to be taken into account as input for the present simplifIed model are the solar heat gains and the heat flows Into the room from the external surface.

6.5 Dynamic building simulation programs

For all cases which are not ii the range of vaildation of the simplified methods. TABS calculations have to be carried out by means of a detailed dynamic building-system model.

These TABS calculations have to take into account the water flow into the pipes, the heat conduction between upward and downward surface of the slab and the pipe level, heat conduction of each wall, mutual radiation between internal surfaces, convection with air, and the thermal balance of the aw

Whenever results of TABS calculations are reported, the computer pwgram applied shall be specified.

7 Input for computer simulations of energy performance

To facilitate dynamic computer simulations of buildings wim embedaed radiant heating and cooling systems. the equivalent resistances between the heat conduction layer (pipe level) and the upward and downward surfaces can be used.

For type E, F, and G systems in ISO 11855-1, this resistance is dwectly calculated. Both the equivalent iiward and outward resistance is calculated.

For type A, B, C and D systems (in ISO 11855-1 and EN 1264-2 and EN 1264.5) the equivalent resistance is calculated from the inward specific heat flow. q. and outward speetfic heat flow, qu. taking into account the surface resistance according to this equation:

Based on the simplified calculation method in 64. the following diagrams for design of a TABS have been developed. The diagram in Figure A.2 shows an example of the relation befween internal heat gains, water si.ipply temperature, heat transfer on the room side, hours of operation and heat transfer on the water side. The diagrams correspond to a concrete slab shown in Figure A.1 with a solid concrete floor, ooriductrvity 1,2 WI(m-K), pipe spacing of 0.15 m and a permissdle room temperature range of 21 C to 26C.

The upper diagram In Figure A.2 shows on the V-axis the maximum permissible total heat gain In space

(Internal gains plus solar gains) [Wim2). and on the X-axis the requwed water supply temperature. The lines In

the d.aram correspond to different hours of operation (8 h, 12 h, and 24 h) and different daily energy gains

(Wh/(m -dfl.

The lower diagram in Figure A.2 shows the cooling power (W!m2J required on the water side (to size the chiller) foe’ TAS as a function of water supply temperature and operation time Further, the amount of energy rejected per day is indicated [Wh/(rn d)J.

The example shows that by a maximum internal heat gain of 48 W/m2 and 8 h operation, a supply water temperature of 17,8 C is requied. If, instead, the system is in operation for 24 h, a supply water temperature of 21.3 C is required. In total, the amount of energy rejected from the room is approximately. 460 Wh/m2 per day. The required cooling power on the water side is for 8 h operation 58 Wim and for 24 h operation only 20 W/m2 Thus, for a 24 Ii operation, the chiller can be much smaller.