Method and system for controlled cooling of small milk quantities

A system for controlled cooling of small milk quantities (milk spots) entering, with time intervals, a milk cooling tank (2) having at least a bottom wall portion (12) comprising, on the milk contacting side thereof, a milk cooling surface (12′) being part of an evaporator (4) in a cooling circuit, the tank containing an agitator means (19) being provided for agitation of the milk in the tank;

• a means (10) for measuring the milk quantity in the tank;
• said cooling circuit comprising, in series therein, the evaporator (4);
• a motor (13)-driven compressor (5) being connected to a refrigerant outlet (6) from the evaporator, and, through an interconnected condenser (7) and an expansion valve (8) downstream thereof, to a refrigerant inlet (9) to the evaporator (4), characterized by
• a temperature transducer (11) for monitoring the milk temperature in the tank, control means regulating the operation of the cooling equipment in dependence of the vaporizing pressure when there is a small milk volume in the milk cooling tank (2) and the agitator means (19) cannot work properly, and a vapour pressure sensor (17;40),
• a control equipment (18;23;33;
• 41) being connected to the temperature transducer (11), for receiving a temperature input, and being connected to the motor (13) driving the compressor (5) for regulating same, and by a temperature sensor (16), which is connected between the evaporator outlet (6) and compressor inlet and senses the temperature of the vapour flow there between, serving to control the expansion valve (8), and
• the pressure sensor (17;
• 40), is connected between the temperature sensor (16) and compressor inlet and serves to sense the pressure of the vapour and submits an output signal to the control equipment (18;
• 41) said system controlling the temperature of the refrigerant in the evaporator by regulating the vaporizing pressure, so that the temperature of the milk contacting cooling surface (12′) is always at least slightly higher than 0° C., whereas the refrigerant temperature in the evaporator (4) is below 0° C., when the compressor is running.