A refrigeration and heating apparatus comprises a refrigerated bulk fluid tank 5, refrigeration means 7 for refrigerating or heating fluid stored in the tank, and at least one four-way valve 88 in fluid communication with the refrigeration means. The four-way valve comprises a first port 89, a second port 90, a third port 91, a fourth port 92, and a valve member (93, fig.8a & fig.8b) movable between a first position and a second position. In the first position, fluid flows along a first flow path (94, fig.8a) between the first port and the second port, and along a second flow path (95, fig.8a) between the third port and the fourth port. In the second position, fluid flows along a third flow path (96, fig.8b) between the first port and the fourth port, and along a fourth flow path (97, fig.8b) between the third port and the second port. In use, the apparatus provides refrigeration and heating of bulk fluids, preferably relating to the refrigeration and heating of bulk milk freshly obtained from dairy animals, such as cows.
