1.1 EXPERIMENTS

1.1.1 SYSTEM DESIGN

Two small low flow SDHW systems were tested side-by-side in a laboratory test facility for solar heating systems. With the exception of the solar tank the systems were identical.

Fig. 1 shows schematic illustrations of the two tanks. Both tanks are standard mantle tanks suitable for low flow systems. In both tanks the auxiliary energy is supplied by electric heating elements.

One tank is equipped with a PEX pipe for hot water draw-off from the very top of the tank. The other tank is equipped with two PEX pipes for hot water draw-off from the very top of the tank and from the middle of the tank.

A three way valve, type RAVI from Danfoss A/S, ensures that the temperature of the tapped water during draw-offs is equal to the required hot water temperature. If this is not possible due to high tank temperatures, the valve ensures that the difference between the tapped water temperature and the required hot water temperature is as low as possible. That is, the three way valve ensures that the right part of the hot water is tapped from the top and from the middle of the tank.

The most important data of the tested systems are given in Table 1. Fig. 2 shows the collectors of the tested systems.

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