Spray refrigeration system for low temperature-sensitive product

Claim 2

In a method for the intransit refrigeration of freezesensitive products supported on a metal base in a thermally insulated closeable storage chamber by over head spraying a cryogenic fluid having a boiling point at atmospheric pressure below about -20* F. in response to gas temperature monitoring within the storage chamber so as to maintain the storage chamber gas temperature below a chamber temperature predetermined upper limit, the improvement comprising: sensing the ambient temperature outside said storage chamber and commencing the introduction of heat into said storage chamber through said metal base in response to such ambient temperature sensing when said ambient temperature is within 5*F. of said chamber gas temperature upper limit and at average density of 1-15 watts per square foot of metal base area and at rate higher than the rate at which heat flows through the chamber walls to the ambient air so as to maintain the chamber inner wall at temperature not substantially colder than the sensed chamber gas temperature, and transferring part of such heat to the sprayed cryogenic fluid.

Claim 3

A method according to claim 1 wherein heat is introduced into said storage chamber in at least two increments with the first heat increment introduced when said ambient temperature is within 5*F of said chamber gas temperature upper limit and a second heat increment introduced when said ambient temperature is more than 5*F below said chamber temperature upper limit.

Claim 4

A method according to claim 1 wherein heat is introduced to said storage chamber when the ambient temperature is slightly above the chamber temperature upper limit.

Claim 5

A method according to claim 1 for the intransit refrigeration of fresh meat, wherein the chamber temperature upper limit is 32*F. and heat is introduced to said storage chamber when the ambient temperature is below 30* F.

Claim 6

A method according to claim 1 for the intransit refrigeration of leaf vegetables, wherein the chamber temperature upper limit is 38*F. and heat is introduced to said storage chamber when the ambient temperature is below 33*F.

Claim 7

A method according to claim 1 for the intransit refrigeration of bananas, wherein the chamber temperature upper limit is 56*F. and heat is introduced to said storage chamber when the ambient temperature is below 54*F.

Claim 8

Apparatus for the intransit refrigeration of freeze-sensitive products comprising in combination: a. a closeable storage chamber for said products surrounded by thermal insulation sufficient to reduce heat transfer below 0.1 Btu/hr X ft2 X * F.; b. a thermally insulated container associated with the storage chamber for storing pressurized liquefied gas having a boiling point at atmospheric pressure below about -20* F.; c. spray conduit means positioned within the upper portion of said storage chamber for discharging a multiplicity of discrete cold fluid streams into the storage chamber; d. liquefied gas flow control means comprising a gas temperature sensing element positioned within said storage chamber, a fluid discharge conduit between the liquefied gas container (b) and spray conduit means (c), a flow control valve in said fluid discharge conduit, and signal transmitting means from said gas temperature sensing element to said control valve for controllably releasing liquefied gas from said container through said spray conduit means into said storage chamber when the sensed temperature is in a predetermined range with a refrigeration release temperature upper limit; e. a metal base in the floor of said storage chamber extending substantially the entire length and width thereof for supporting the product; f. a multiplicity of electrical resistance heating elements positioned in spaced rElationship beneath said metal base (e) in heat transfer relation therewith each extending the entire length of said metal base; g. power source means for said electrical resistance heating elements; h. an ambient air temperature sensing element outside said storage chamber and signal transmitting means from said element to said power source for activating at least some of said electrical resistance heating elements when said ambient air temperature drops to within 5*F. of said refrigeration release temperature.

Claim 9

Apparatus for the intransit refrigeration of freeze-sensitive products comprising in combination: a. a closeable storage chamber for said products surrounded by thermal insulation sufficient to reduce heat transfer below 0.1 Btu/hr X ft2 X * F.; b. a thermally insulated container associated with the storage chamber for storing pressurized liquefied gas having a boiling point at atmospheric pressure below about -20* F.; c. spray conduit means positioned within the upper portion of said storage chamber for discharging a multiplicity of discrete cold fluid streams into the storage chamber; d. liquefied gas flow control means comprising a gas temperature sensing element positioned within said storage chamber, a fluid discharge conduit between the liquefied gas container (b) and spray conduit means (c), a flow control valve in said fluid discharge conduit, and signal transmitting means from said gas temperature sensing element to said control valve for controllably releasing liquefied gas from said container through said spray conduit means into said storage chamber when the sensed temperature is in a predetermined range with a refrigeration release temperature upper limit; e. a metal base in the floor of said storage chamber extending substantially the entire length and width thereof for supporting the product; f. a multiplicity of electrical resistance heating elements positioned in spaced rElationship beneath said metal base (e) in heat transfer relation therewith each extending the entire length of said metal base; g. power source means for said electrical resistance heating elements; h. an ambient air temperature sensing element outside said storage chamber and signal transmitting means from said element to said power source for activating at least some of said electrical resistance heating elements when said ambient air temperature drops to within 5*F. of said refrigeration release temperature.

Claim 10

Apparatus according to claim 7 with a multiplicity of ambient air temperature sensing elements, a multiplicity of ambient air temperature sensing elements, a multiplicity of signal transmitting means each joined to a different temperature sensing element and arranged with electrical resistance heating elements such that a first set of heating elements are activated when the sensed ambient air drops to a first temperature and a second set of heating elements are activated when the sensed ambient air drops to a second temperature below said first temperature.

Claim 11

Apparatus according to claim 8 with three ambient air temperature sensing elements and three set of heating elements connected such that the first set of heating elements is activated when the sensed ambient air drops to 30*F., the second set of heating elements is additionally activated when the ambient air temperature drops to 15*F., and the third set of heating elements is still additionally activated when the ambient air temperature drops to -5*F.

Claim 12

Apparatus according to claim 7 wherein the electric power source is three phase and the electrical resistance heating elements are connected in a delta arrangement.

Claim 13

Apparatus according to claim 7 wherein the electric power source is three phase, with a multiple of three electrical resistance heating elements.

Claim 14

Apparatus according to claim 7 wherein said metal base is supported above the inner wall of the storage chamber by a multiplicity of transversely spaced metal members extending the entire length of said chamber, and said electrical resistance heating elements are located between some adjacent pairs of longitudinal members in contiguous relation therewith.

Claim 15

Apparatus according to claim 12 wherein a multiplicity of longitudinally aligned aluminum extrusions comprise said metal base and transversely spaced metal members, each extrusion having an upper panel section with adjacent panel edges longitudinally bonded to each other, and also having longitudinally extending lower sections of inverted T- cross-section and bottom end attached to the inner wall of said storage chamber.