Environmentally controlled chamber system utilizing hydrocarbon refrigerants
An environmentally controlled chamber system. The system includes an insulated enclosure having an access door and a humidification/dehumidification chamber enclosure arranged and disposed to provide humidification or dehumidification to the insulated enclosure. The system also includes a refrigerant loop having an enclosure evaporator, a dehumidification evaporator, at least one condenser, a variable speed compressor and piping for directing refrigerant from the variable speed compressor to the enclosure evaporator, the dehumidification evaporator, and the at least one condenser. An electrical heating element is arranged and disposed adjacent to the enclosure evaporator to selectively provide heat to at least a portion of the enclosure evaporator. A method for controlling the environmentally controlled chamber system is also disclosed.
1 . An environmentally controlled chamber system comprising:
an insulated enclosure having an access door;
a humidification/dehumidification chamber enclosure arranged and disposed to provide humidification or dehumidification to the insulated enclosure;
a refrigerant loop comprising:
an enclosure evaporator, a dehumidification evaporator, at least one condenser, a variable speed compressor, a controller, and piping for directing refrigerant from the variable speed compressor to the enclosure evaporator, the dehumidification evaporator, and the at least one condenser; and
an electrical heating element having a first electrical heating element positioned on the bottom and in contact with the enclosure evaporator, the first electrical heating element being arranged and disposed adjacent to the enclosure evaporator with little or no exposure to an induced airflow to selectively provide heat to at least a portion of the enclosure evaporator and a second electrical heating element positioned such that the induced airflow goes over the enclosure evaporator prior to going over the second heating element;
wherein the controller is configured to energize one or both of the first electrical heating element and the second electrical heating element to offset cooling of the enclosure evaporator during operation of the variable speed compressor.
2 . The system of claim 1 , wherein the refrigerant is a hydrocarbon refrigerant.
3 . The system of claim 2 , wherein the hydrocarbon refrigerant is selected from the group consisting of R290 or R600a, hydrofluorocarbon/hydrocarbon hybrid refrigerants and combinations thereof.
4 . The system of claim 2 , wherein the refrigerant loop contains less than 500 g of refrigerant.
5 . The system of claim 2 , wherein the refrigerant loop contains less than 150 g of refrigerant.
6 . The system of claim 2 , wherein the first electrical heating element is positioned above a condensate pan.
7 . The system of claim 1 , wherein the second heating element is mounted on a diffuser.
8 . The system of claim 2 , wherein the first electrical heating element passes through an interior portion of the enclosure evaporator.
9 . The system of claim 7 , wherein the diffuser is arranged and disposed to permit flow of air therethrough.
10 . The system of claim 1 , wherein the humidification/dehumidification chamber enclosure is positioned outside of the insulated enclosure and is arranged with componentry capable of providing humidification and dehumidification, the componentry including a water level sensing valve, a multiplicity of ultrasonic humidification elements, and the dehumidification evaporator.
11 . The system of claim 2 , further comprising an air inlet tube and an air outlet tube to direct air through the humidification/dehumidification chamber enclosure, wherein the placement of the air inlet tube and the air outlet tube utilizes a pressure differential between the air inlet side and air outlet side of the enclosure evaporator to induce the induced airflow through the humidification/dehumidification chamber enclosure.
12 . The system of claim 2 , further comprising a condensate loop downstream from the variable speed compressor to provide de-superheat, system durability and condensate control.
13 . The system of claim 2 , further comprising a hydrocarbon sensor arranged and disposed to detect hydrocarbon leaks from the refrigerant loop.
14 . A method of controlling an environmentally controlled chamber system comprising:
providing an environmentally controlled chamber system comprising:
insulated enclosure having an access door;
a humidification/dehumidification chamber enclosure positioned outside of the insulated enclosure and arranged and disposed to provide humidification or dehumidification to the insulated enclosure;
a refrigerant loop comprising:
an enclosure evaporator, a dehumidification evaporator, at least one condenser, at least one variable speed compressor and piping for directing refrigerant from the at least one variable speed compressor to the enclosure evaporator, the dehumidification evaporator, and the at least one condenser; and
an electrical heating element having a first electrical heating element positioned on the bottom and in contact with the enclosure evaporator, the first electrical heating element being arranged and disposed adjacent to the enclosure evaporator, the first electrical heating element having little or no exposure to an induced airflow and a second electrical heating element positioned such that the induced airflow goes over the enclosure evaporator prior to going over the second heating element;
directing the refrigerant to a high-pressure differential between inlet and outlet and modulation of the refrigerant flow going to the dehumidification evaporator or the dehumidification evaporator with one or more valves; and
heating at least a portion of the enclosure evaporator by energizing one or both of the first electrical heating element and the second electrical heating element to offset cooling of the enclosure evaporator during operation of the variable speed compressor.
15 . The method of claim 14 , wherein the heating of at least a portion of the enclosure evaporator with the electrical heating element includes selective heating of the first heating element and the second heating element.
16 . The method of claim 15 , wherein the heating of at least a portion of the enclosure evaporator with the electrical heating element includes heating of the first heating element and the second heating element individually or simultaneously via proportional voltage or amperage control.
17 . The method of claim 15 , further dehumidifying air for the enclosure with the enclosure evaporator while providing controlled heating to the enclosure evaporator with the first heating element and the second heating element.
18 . The method of claim 14 , wherein the refrigerant is a hydrocarbon refrigerant.
19 . The method of claim 18 , wherein the hydrocarbon refrigerant is selected from the group consisting of R290 or R600a, hydrofluorocarbon/hydrocarbon hybrid refrigerants and combinations thereof.
20 . The method of claim 18 , wherein the refrigerant loop contains less than 500 g of refrigerant.
21 . The method of claim 18 , wherein the refrigerant loop contains less than 150 g of refrigerant.
22 . The method of claim 14 , wherein the heating of the at least a portion of the enclosure evaporator is devoid of hot gas heating.
23 . The method of claim 14 , wherein the temperature of the enclosure is maintained to ±0.5° C. of air exiting a plenum and within the enclosure.
24 . The method of claim 14 , wherein the humidity of the enclosure is maintained within ±1.0% to 3.0% relative humidity, depending on setpoint, within the enclosure.