Thermostatic valves

Thermostatic valves (Tevs) for such chains embody the mechanism that determines the overheating of this gas from the evaporator (Fig. 8.1). Refrigerant boils in the evaporator with TE and pe, until it is completely a couple of points and then superheats the state, Ts, pe, in which she goes to the suction line, point B. a separate container of the same refrigerant temperature Ts will pressure (ps)and the difference ps - face pe C-B in Fig. 8.1 signal depends on the number of overheating.

The main thermostatic expansion valve (Fig. 8.2) has detector and battery to charge the same as the refrigerant in the circuit. Pressure (ps)generated in the flask with the hot gas passes through a capillary tube to the top of the diaphragm. Adjustable spring provides a balance of PS - pe on the diaphragm and valve stem (attached in the center. In the case of overheating, the fall for any reason, there will be a risk of fluid achievements of the compressor. Ts will be reduced accordingly fell in ps. Forces on the diaphragm, now out of balance and spring will close the valve.

Conversely, if the load on the evaporator increases, refrigerant evaporates earlier and is more overheating in the vessel position. Then PS will grow and open the valve wider to meet new requirements.

Bottles should have a greater potential than other battery or charging, it may take all valve capsule and the tube, if they colder. If this happens, flasks on TP " will only contain vapours and will not be responsible position, Ts, ps on Tp curve.

You can also use this last effect. The battery can be charged limit refrigerant inside it evaporates at a specified temperature (usually 0C). Above this point, the pressure inside it will cease to stick to the boiling point of the curve, but will follow the gas laws, as shown in Fig. 8.3.

P1/P2 = T1/T2

and the valve will remain closed. This is done to limit the pressure in the evaporator when you first start warm system that may overload the motor. This is called the limit of the charge or the maximum working pressure. Such valves should be installed so that the phial is the coldest part.

The slope of Tp curve is not constant, so that the fixed spring pressure will increase overheating at higher operating temperatures. To provide this functionality and provide a valve which can be used in wide variety of applications, the bottle can be accused of a mixture of two or more volatile liquids, to modify the characteristics of the curve.

Some manufacturers use the principle of adsorption of gas through porous materials such as silica gel or charcoal. With the adsorbent is firm and cannot migrate from flask, these valves do not suffer restoration of the charge.....