The first and second refrigeration systems are prefer- lower region 50. Thus, the heating elements 52 and side ably vapor-compression refrigeration systems. The first panels 36 constitute means for heating the circulating refrigeration system includes a first evaporator 28 adja- air as the air is forced from the first region to the second cent an upper region of the first compartment 24, a first region.
compressor, a first condenser, and a first expansion 5 Humidity is controlled during heating of the first valve. The first compressor, first condenser, and first compartment 24 so that heating does not result in foods expansion valve are collectively designated generally as are too dry or too soggy. Humidity is controlled by a 30 (see FIG. 2). The second refrigeration system in- water heater 60 adjacent the upper region 4*. The water eludes a second evaporator 32 adjacent an upper region heater 60 includes a water reservoir 62 and a water of the second compartment 26, a second compressor, a 10 heating element 64, constituting means for heating second condenser, and a second expansion valve. The water within the reservoir 62. Water, heated in the second compressor, second condenser, and second ex- reservoir 62, evaporates into the circulating air to inpansion valve are collectively designated generally as crease the humidity of the air in that location to near 34. The first refrigeration system constitutes means for saturation. The moist air is then heated by the hot side refrigerating the first compartment 24 to a temperature 15 panels 36 and forced through the first compartment, below ambient temperature. The second refrigeration Heating of the air by the hot side panels 36 increases the system constitutes means for refrigerating the second air's dry bulb temperature. The air, as it is circulated compartment 26 to a temperature below ambient tern- through the first compartment, has a dry bulb temperaperature. ture in excess of its wet bulb temperature. Thus, the
As shown in FIG. 5, the first compartment 24 is de- 20 water heater 60 comprises means for inducing humidity fined between opposing vertical side walls or panels 36, in the circulating air as it flows adjacent the return ducts a vertical back wall 38, a horizontal upper panel 40, and 56 to add moisture to the circulating air before the air is a horizontal lower panel 42. The side walls 36 and pan- returned to the upper region 48 and before the returned els 40 and 42 have outer edges which define a forwardly air is heated by the heating elements 52. facing opening 44. A door 46 (shown in FIGS. 1 and 2) 25 The ducts 56 include vertical side panels 66 spaced is hinged to the cabinet 22 for covering the opening. from the heating elements 52. Sealed air spaces 68 beThe first compartment 24 includes an upper region 48, tween the heating elements 52 and side panels 66 insuconstituting a first region, and a lower region 50, consti- late the ducts 56 so that the ducts are not substantially tuting a second region. The heating system comprises heated by the heating elements 52. The circulating air is heating elements 52 contacting the side panels 36. Pref- 30 not heated as it passes through the ducts 56. And since erably, the heating elements 52 are rope foil heaters, the ducts 56 are cool prior to the heating operation and such as those manufactured by Ocean States Thermon- cooler than the circulating air, the circulating air actutics, of Johnston, R.I. The heating elements 52 have a ally cools somewhat in the ducts 56 during initial heatfoil backing. The foil backing is secured by adhesive to ing operation. Preferably, the panels forming the ducts the outer surface of each side panel 36 so that the heat- 35 56 are sufficiently thick, e.g., twenty-four gauge staining elements 52 contact the panels 36. Preferably, the less steel, so that temperature of food heated in the first heating elements 52 contact the panels 36 along nearly compartment 24 increases at a faster rate than the ducts the entire lengths of the panels 36. The heating elements 56. In other words, the thermal lag of the ducts 56 is 52 heat the side panels 36 which, in turn, heat the first greater than the thermal lag of the food. Thus, the dry compartment 24. The heating elements 52 constitute 40 bulb temperature of the circulating air as it passes over means for heating the first compartment to a tempera- the water heater 60 is cooler than when it passes over ture above ambient temperature. the food in the first compartment 24. Since the wet bulb
A first fan (or blower) 54, adjacent the upper region temperature of the circulating air cannot be greater than 48, forces air through the first compartment 24 from the its coolest dry bulb temperature and since the dry bulb upper region 48 to the lower region 50. Return air ducts 45 temperature of the air is warmer as it passes over the 56, along the sides of the first compartment 24, return food than when it passes over the water heater 60, then circulating air, forced by the fan 54 to the lower region moisture in the circulating air will not condense on the 50, back to the upper region 48. Thus, the fan 54 consti- food. At the end of the heating operation the difference tutes means for circulating air through the first com- between the dry bulb and wet bulb temperatures of the partment 24. Operation of the fan 54 results in forced 50 circulating air in the first compartment decreases. This convection cooling during cold storage of foods in the difference decreases because moisture is constantly first compartment 24 and results in forced convection being added to the circulating air by the water heater heating during heating of such foods. During operation 60. Condensation of moisture on the food, however, is of the first refrigeration system, circulating air passes not a problem once the temperature of the food apthrough and is cooled by the first evaporator 28. The 55 proaches the dry bulb temperature of the circulating air. cool air is forced by the fan 54 through side openings 58 As the food's temperature increases, moisture will not adjacent the upper panel 40, then forced from the upper condense on the food even if the humidity of the circuregion 48 to the lower region 50 to cool food stored lating air approaches saturation. However, if the circuwithin the compartment 24. The circulating air is then lating air is too dry during the final heating of the food, forced from the lower region 50, through the ducts 56 60 excessive moisture will evaporate from the food and the and returned to the evaporator 28. This air is constantly food will be undesirably dry. By inducing humidity in recirculated during operation of the first refrigeration the circulating air before the air is heated by the heating system During operation of the heating system, the first elements 52, moisture will not condense on the food nor refrigeration system is deactivated and the air is circu- will the food become dry.
Iated by the fan 54 the same as during cooling of the first 65 The first compartment 24 contains a plurality of verticompartment 24. The heating elements 52 heat the side cally spaced, horizontally extending trays (or shelves) panels 36. The circulating air is heated as it passes over 70 for holding food (designated generally as F) placed the hot side panels 36 from the upper region 48 to the within the first compartment 24. Each shelf 70 is slide