Experimental Case Study - Design for Micro-Combined Cooling, Heating and Power Systems - page 368

Fig. 17 Hydraulic circuit of pellet boiler (CH1)

To protect from overheating the Stirling engine and to operate the thermal chiller
two additional cooling circuits have been used in the hydraulic scheme. They are
connected to the equipment through heat exchangers. All circuits have safety valve
(not shown in Fig. 16 ), with the role of protection from the increase of pressure in
the circuit over the maximum calibrated value. Thus was obtained the 12 hydraulic
circuits, which will be described below.
Circuit of hot water from pellet boiler to hot water tank (CH1)
This hydraulic circuit connects the pellet boiler to the hot water tank (Fig. 17 ).
The heat resulting from the burning of the pellets is taken up with the aid of an
internal heat exchanger (inside of the boiler) and sent to the tank. The thermal agent
used is pressurized water nonharsh.
In this hydraulic circuit besides the recirculation pump there are a mixing valve,
used to control the start temperature of the tank (to reduce the duration of the
transition mode and thus reduce the quantity of ash and smoke sent toward the
chimney) and a three-way valve, through which the work area in the hot water tank
is chosen, depending on the temperature of the water at the bottom of the tank (at
different strati ed temperatures values of the tank).

Circuit of hot water from heat storage to the chiller (CH2)
The chiller has three outlets in its inner structure, all of which are coupled
thermally:

High temperature input (HT),

￿

Medium temperature rejection output (MT),

￿

Low temperature output (LT).

￿