Floor Heating

8.9.7.1 General

Floor heating in industrial premises usually means hot-water pipes placed inside the concrete floor. (Electric coils or electric sheets are also used in non­industrial premises; this is, however, not treated here.) Figure 8.60 shows a typical installation of heatpipes inside the floor. Note that the pipes are placed relatively deep down inside the concrete to help even out the surface tempera­ture.

Floor heating has several advantages:

The heat is supplied at the floor, where it normally is most needed.

Putting heating coils or heating pipes into a concrete floor makes a heat reservoir that helps even out temperature fluctuations.

When using hot-water pipes in the floor, the water temperature is usually low (30 °C — 40 °C), so the system is well suited for low-temperature heating.

The system is noiseless and draft-free.

8.9.7.2 Surface Temperature and Heat Emission

One limitation in the use of floor heating is the surface temperature of the floor. Most people will find a floor surface temperature of more than 25 °C uncomfortable.

Heat is transmitted from the floor to the room by radiation and convec­tion. For practical purposes, we can put the heat transfer coefficient to 8 W/m2 °C. Based on this assumption, we can make the diagram in Fig. 8.61.

FIGURE 8.59 Mixing jet ventilation. Many nozzles blow the air horizontally 3nd vertically,

I SO mm

Insulation

200 mm

SO mm

FIGURE 8.60 Arrangement and typical dimensions of hot-water pipes in a concrete floor.

Surface temperature of the floor [°C] 30

25 20 15 10 5

40 60 80 100 120 Heat transfer, Q [W/m2| Heat transfer from a heated floor versus room and floor temperatures.

20

FIGURE 8.61

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