Electronic temperature control system

Claim 2

A refrigeration control system for a refrigeration system including a refrigerated display case with a primary air conduit having an air outlet opening and an air inlet opening, an evaporator coil arranged within the primary air conduit for refrigerating air passing through such conduit, and an expansion valve coupled to the inlet end of the evaporator coil, said refrigeration control system comprising: a pressure sensing means arranged at the refrigerant discharge line from the evaporator coil for sensing the pressure (P) of the refrigerant within such discharge line; means for determining the saturation temperature (T sat ) of the refrigerant from the measurement of pressure P; means for setting a level of superheat (T sh ) desired within the refrigerant discharged from the evaporator coil and setting a desired temperature (T 2set ) for such discharge refrigerant by T.sub.2set =T.sub.sat +T.sub.s ; a second temperature sensing means arranged adjacent to the refrigerant discharge line from the evaporator coil for measuring the temperature (T 2 ) of the refrigerant discharged from the evaporator coil; comparator means for comparing temperature T 2 with temperature T 2set and providing an output comparison signal if T 2 <T 2set ; and, control means receiving the output comparison signal and providing an output control signal for controlling operation of the refrigeration system for maintaining temperature T 2 equal to or above temperature T 2set .

Claim 3

A refrigeration control system according to claim 1 wherein said means for determining the saturation temperature T sat from pressure P uses the following relationships ______________________________________ For refrigerant R-502 Temperature Range -50 to 0° F. T.sub.sat = 0.00053204591P.sup.3 - 0.07027440492P.sup.2 + 4.2630221429P - 98.92133288 Temperature Range 0° F. to 50° F. T.sub.sat = 0.000031298402P.sup.3 - 0.01112645218P.sup.2 + 1.8907849084P - 66.2388444 For refrigerant R-12 Temperature Range -10 to +50° F. T = 0.00025752709P.sup.3 - 0.04544987P.sup.2 + 3.7152263P - 66.375648 For refrigerant R-22 Temperature Range -10 to +50° F. T = 0.00006161138P.sup.3 - 0.017536207P.sup.2 + 2.3158884P ______________________________________ - 67.003218

Claim 4

A refrigeration control system according to claim 1 wherein temperature T sh is set to be a minimum of approximately 5° F.

Claim 5

A refrigeration control system according to claim 1 further comprising third temperature sensing means arranged adjacent the inlet end of the evaporator coil for sensing the temperature (T 3 ) of the refrigerant flowing into the evaporator coil and wherein said control means provides an output control signal for controlling operation of the refrigeration system for maintaining temperature T 2 greater than temperature T 3 .

Claim 6

A refrigeration control system according to claim 4 wherein said control means provides an output signal for controlling the operation of the refrigeration system for maintaining temperature T 2 greater than temperature T 3 by an amount sufficient to insure that all of the liquid refrigerant passing through the evaporator coil is completely transformed into a gaseous refrigerant by the time that it is discharged from the evaporator coil.

Claim 7

A refrigeration control system for a refrigeration system including a refrigerated display case with a primary air conduit having an air outlet opening and an air inlet opening, an evaporator coil arranged within the primary air conduit for refrigerating air passing through such conduit, and an expansion valve coupled to the inlet end of the evaporator coil, said refrigeration control system comprising: first temperature sensing means arranged at the air discharge side of the evaporator coil for sensing the temperature (T 1 ) of the air that has passed over the evaporator coil; a second temperature sensing means arranged adjacent to the refrigerant discharge end of the evaporator coil for measuring the temperature (T 2 ) of the refrigerant discharged from the evaporator coil; comparator means for comparing temperature T 1 with temperature T 2 to determine if temperature T 1 is greater than temperature T 2 by a preselected temperature differential; means for setting a desired temperature differential between temperature T 1 and temperature T 2 for maintaining temperature T 1 sufficiently above temperature T 2 to assure that the refrigerant discharged from the evaporator coil is above its saturation temperature; and, control means to provide an output control signal for controlling operation of the refrigeration system for maintaining temperature T 1 sufficiently above temperature T 2 by at least the set temperature differential.

Claim 8

A refrigeration control system for a refrigeration system including a refrigerated display case with a primary air conduit having an air outlet opening and an air inlet opening, an evaporator coil arranged within the primary air conduit for refrigerating air passing through such conduit, and an expansion valve coupled to the inlet end of the evaporator coil, said refrigeration control system comprising: first temperature sensing means arranged at the air discharge side of the evaporator coil for sensing the temperature (T 1 ) of the air that has passed over the evaporator coil; a second temperature sensing means arranged adjacent to the refrigerant discharge end of the evaporator coil for measuring the temperature (T 2 ) of the refrigerant discharged from the evaporator coil; comparator means for comparing temperature T 1 with temperature T 2 to determine if temperature T 1 is greater than temperature T 2 by a preselected temperature differential; means for setting a desired temperature differential between temperature T 1 and temperature T 2 for maintaining temperature T 1 sufficiently above temperature T 2 to assure that the refrigerant discharged from the evaporator coil is above its saturation temperature; and, control means to provide an output control signal for controlling operation of the refrigeration system for maintaining temperature T 1 sufficiently above temperature T 2 by at least the set temperature differential.

Claim 9

A refrigeration control system according to claim 6 further comprising third temperature sensing means arranged adjacent the inlet end of the evaporator coil for sensing the temperature (T 3 ) of the refrigerant flowing into the evaporator coil and wherein said control means provides an output control signal for controlling operation of the refrigeration system for maintaining temperature T 2 greater than temperature T 3 .

Claim 10

A refrigeration control system according to claim 7 wherein said control means provides an output signal for controlling the operation of the refrigeration system for maintaining temperature T 2 greater than temperature T 3 by an amount sufficient to insure that all of the liquid refrigerant passing through the evaporator coil is completely transformed into a gaseous refrigerant by the time that it is discharged from the evaporator coil.

Claim 11

A refrigeration control system according to claim 6 wherein temperature T 1 is maintained a minimum of 4° to 6° F. above temperature T 2 for freezer display cases.

Claim 12

A refrigeration control system according to claim 6 wherein temperature T 1 is maintained a minimum of 5° to 8° F. above temperature T 2 for medium temperature display cases.

Claim 13

A refrigeration control system according to claim 6 wherein temperature T 1 is maintained a minimum of approximately 5° F. above temperature T 2 .

Claim 14

A refrigeration control system according to claim 11 further comprising an electronically controlled expansion valve and wherein said control means provides an output signal for closing said expansion valve if (T 1 -T 2 )<5° F. for longer than a preselected time period.

Claim 15

A refrigeration control system according to claim 6 wherein said first temperature sensing means for measuring the air discharge temperature (T 1 ) is arranged in the primary air conduit of the refrigerated display case at a location downstream of the evaporator coil.

Claim 16

A refrigeration control system according to claim 6 further comprising an electronically controlled expansion valve, means for setting a desired temperature (T 1set ) for the air discharge temperature, and further comparator means for comparing temperature T 1 with temperature T 1set ; and wherein said control means is coupled to the output of said further comparator means and provides an output signal for opening the expansion valve if (T 1 -T 1set )>1° F. and an output signal for closing the expansion valve if (T 1 -T 1set )<1° F.

Claim 17

A refrigeration control system according to claim 6 further comprising means for setting an alarm temperature (T A ) and wherein said control means provides an alarm signal if T 1 >T A for longer than a set period of time.

Claim 18

A refrigeration system comprising: a refrigerated display case with a primary air conduit having an air outlet opening and an air inlet opening; an evaporator coil arranged within said primary air conduit for refrigerating air passing through said primary air conduit; an electronically controlled expansion valve coupled to the inlet end of said evaporator coil; and, a refrigeration control system including: first temperature sensing means arranged at the air discharge side of said evaporator coil for sensing the temperature (T 1 ) of the air that has passed over said evaporator coil; a second temperature sensing means arranged adjacent to the refrigerant discharge end of said evaporator coil for measuring the temperature (T 2 ) of the refrigerant discharged from said evaporator coil; comparator means for comparing temperature T 1 with temperature T 2 to determine if temperature T 1 is greater than temperature T 2 by a preselected temperature differential; means for setting a desired temperature differential between temperature T 1 and temperature T 2 for maintaining temperature T 1 sufficiently above temperature T 2 to assure that the refrigerant discharged from said evaporator coil is above its saturation temperature; and, control means to provide an output control signal to said electronically controlled expansion valve for controlling operation of the refrigeration system for maintaining temperature T 1 sufficiently above temperature T 2 by at least the set temperature differential.

Claim 19

A refrigeration system comprising: a refrigerated display case with a primary air conduit having an air outlet opening and an air inlet opening; an evaporator coil arranged within said primary air conduit for refrigerating air passing through said primary air conduit; an electronically controlled expansion valve coupled to the inlet end of said evaporator coil; and, a refrigeration control system including: first temperature sensing means arranged at the air discharge side of said evaporator coil for sensing the temperature (T 1 ) of the air that has passed over said evaporator coil; a second temperature sensing means arranged adjacent to the refrigerant discharge end of said evaporator coil for measuring the temperature (T 2 ) of the refrigerant discharged from said evaporator coil; comparator means for comparing temperature T 1 with temperature T 2 to determine if temperature T 1 is greater than temperature T 2 by a preselected temperature differential; means for setting a desired temperature differential between temperature T 1 and temperature T 2 for maintaining temperature T 1 sufficiently above temperature T 2 to assure that the refrigerant discharged from said evaporator coil is above its saturation temperature; and, control means to provide an output control signal to said electronically controlled expansion valve for controlling operation of the refrigeration system for maintaining temperature T 1 sufficiently above temperature T 2 by at least the set temperature differential.

Claim 20

A refrigeration system according to claim 16 further comprising third temperature sensing means arranged adjacent said inlet end of said evaporator coil for sensing the temperature (T 3 ) of the refrigerant flowing into said evaporator coil and wherein said control means provides an output control signal for controlling operation of the refrigeration system for maintaining temperature T 2 greater than temperature T 3 .

Claim 21

A refrigeration system according to claim 17 wherein said control means provides an output signal for controlling the operation of said electronically controlled expansion valve for maintaining temperature T 2 greater than temperature T 3 by an amount sufficient to insure that all of the liquid refrigerant passing through said evaporator coil is completely transformed into a gaseous refrigerant by the time that it is discharged from said evaporator coil.

Claim 22

A refrigeration system according to claim 16 wherein temperature T 1 is maintained a minimum of 4° to 6° F. above temperature T 2 for freezer display cases.

Claim 23

A refrigeration system according to claim 16 wherein temperature T 1 is maintained a minimum of 5° to 8° F. above temperature T 2 for medium temperature display cases.

Claim 24

A refrigeration system according to claim 16 wherein temperature T 1 is maintained a minimum of approximately 5° F. above temperature T 2 .

Claim 25

A refrigeration system according to claim 21 wherein said control means provides an output signal for closing said expansion valve if (T 1 -T 2 )<5° F. for longer than a preselected time period.

Claim 26

A refrigeration system according to claim 16 wherein said first temperature sensing means for measuring the air discharge temperature (T 1 ) is arranged in said primary air conduit of said refrigerated display case at a location downstream of the evaporator coil.

Claim 27

A refrigeration system according to claim 16 further comprising means for setting a desired temperature (T 1set ) for the air discharge temperature and further comparator means for comparing temperature T 1 with temperature T 1set ; and wherein said control means is coupled to the output of said further comparator means and provides an output signal for opening said expansion valve if (T 1 -T 1set )>1° F. and an output signal for closing said expansion valve if (T 1 -T 1set )<1° F.

Claim 28

A refrigeration system according to claim 16 further comprising means for setting an alarm temperature (T A ) and wherein said control means provides an alarm signal if T 1 >T A for longer than a set period of time.

Claim 29

A refrigeration control system for a refrigeration system including a refrigerated display case with a primary air conduit having an air outlet opening and an air inlet opening, an evaporator coil arranged within the primary air conduit for refrigerating air passing through such conduit, and an expansion valve coupled the inlet end of the evaporator coil, said refrigeration control system comprising: a discharge temperature sensing means arranged adjacent to the refrigerant discharge end of the evaporator coil for measuring the temperature (T 2 ) of the refrigerant discharged from the evaporator coil; an inlet temperature sensing means arranged adjacent the inlet end of the evaporator coil for sensing the temperature (T 3 ) of the refrigerant flowing into the evaporator coil; comparator means for comparing temperature T 2 with temperature T 3 to determine if temperature T 2 is greater than temperature T 3 by a preselected temperature differential; means for setting a desired temperature differential between temperature T 2 and temperature T 3 for maintaining temperature T 2 sufficiently above temperature T 3 to assure that the refrigerant discharged from the evaporator coil is superheated; and, control means to provide an output control signal for controlling operation of the refrigeration system for maintaining temperature T 2 sufficiently above temperature T 3 by at least the set temperature differential.

Claim 30

A refrigeration control system for a refrigeration system including a refrigerated display case with a primary air conduit having an air outlet opening and an air inlet opening, an evaporator coil arranged within the primary air conduit for refrigerating air passing through such conduit, and an expansion valve coupled the inlet end of the evaporator coil, said refrigeration control system comprising: a discharge temperature sensing means arranged adjacent to the refrigerant discharge end of the evaporator coil for measuring the temperature (T 2 ) of the refrigerant discharged from the evaporator coil; an inlet temperature sensing means arranged adjacent the inlet end of the evaporator coil for sensing the temperature (T 3 ) of the refrigerant flowing into the evaporator coil; comparator means for comparing temperature T 2 with temperature T 3 to determine if temperature T 2 is greater than temperature T 3 by a preselected temperature differential; means for setting a desired temperature differential between temperature T 2 and temperature T 3 for maintaining temperature T 2 sufficiently above temperature T 3 to assure that the refrigerant discharged from the evaporator coil is superheated; and, control means to provide an output control signal for controlling operation of the refrigeration system for maintaining temperature T 2 sufficiently above temperature T 3 by at least the set temperature differential.

Claim 31

A refrigeration control system according to claim 26 wherein said control means provides an output signal for controlling the operation of the refrigeration system for maintaining temperature T 2 greater than temperature T 3 by an amount sufficient to insure that all of the liquid refrigerant passing through the evaporator coil is completely transformed into a gaseous refrigerant by the time that it is discharged from the evaporator coil.

Claim 32

A refrigeration control system according to claim 27 wherein temperature T 2 is maintained a minimum of approximately 4° to 10° F. above temperature T 3 .

Claim 33

A refrigeration control system according to claim 28 further comprising an electronically controlled expansion valve, an air temperature sensing means arranged at the air discharge side of the evaporator coil for sensing the temperature (T 1 ) of the air that has passed over the evaporator coil and wherein said control means provides an output signal for closing said expansion valve if (T 1 -T 2 )<5° F. for longer than a preselected time period.

Claim 34

A refrigeration control system according to claim 29 wherein said first temperature sensing means for measuring the air discharge temperature (T 1 ) is arranged in the primary air conduit of the refrigerated display case.

Claim 35

A refrigeration control system according to claim 30 further comprising means for setting a desired temperature (T 1set ) for the air discharge temperature and further comparator means for comparing temperature T 1 with temperature T 1set ; and wherein said control means is coupled to the output of said further comparator means and provides an output signal for opening the expansion valve if (T 1 -T 1set )>1° F. and an output signal for closing the expansion valve if (T 1 -T 1set )<1° F.

Claim 36

A refrigeration system comprising: a refrigerated display case with a primary air conduit having an air outlet and an air inlet opening; an evaporator coil arranged within said primary air conduit for refrigerating air passing through said primary air conduit; an electronically controlled expansion valve coupled to the inlet end of said evaporator coil; and a refrigeration system including: a pressure sensing means arranged at the refrigerant discharge line from said evaporator coil for sensing the pressure (P) of the refrigerant within said discharge line; means for determining the saturation temperature (T sat ) of the refrigerant from the measuring of pressure P; means for setting a level of superheat (T sh ) desired within the refrigerant discharged from said evaporator coil and setting a desired temperature (T 2set ) for such discharge refrigerant by T 2set =T sat +T s ; a second temperature sensing means arranged adjacent to said refrigerant discharge line from said evaporator coil for measuring the temperature (T 2 ) of the refrigerant discharged from said evaporator coil; comparator means for comparing temperature T 2 with temperature T 2set and providing an output comparison signal if T 2 <T 2set ; and, control means receiving the output comparison signal and providing an output control signal for controlling operation of the refrigeration system for maintaining temperature T 2 equal to or above temperature T 2set .

Claim 37

A refrigeration system comprising: a refrigerated display case with a primary air conduit having an air outlet and an air inlet opening; an evaporator coil arranged within said primary air conduit for refrigerating air passing through said primary air conduit; an electronically controlled expansion valve coupled to the inlet end of said evaporator coil; and a refrigeration system including: a pressure sensing means arranged at the refrigerant discharge line from said evaporator coil for sensing the pressure (P) of the refrigerant within said discharge line; means for determining the saturation temperature (T sat ) of the refrigerant from the measuring of pressure P; means for setting a level of superheat (T sh ) desired within the refrigerant discharged from said evaporator coil and setting a desired temperature (T 2set ) for such discharge refrigerant by T 2set =T sat +T s ; a second temperature sensing means arranged adjacent to said refrigerant discharge line from said evaporator coil for measuring the temperature (T 2 ) of the refrigerant discharged from said evaporator coil; comparator means for comparing temperature T 2 with temperature T 2set and providing an output comparison signal if T 2 <T 2set ; and, control means receiving the output comparison signal and providing an output control signal for controlling operation of the refrigeration system for maintaining temperature T 2 equal to or above temperature T 2set .

Claim 38

A refrigeration system according to claim 32 wherein said means for determining the saturation temperature (T sat ) from pressure (P) uses the following relationships ______________________________________ For refrigerant R-502 Temperature Range -50 to 0° F. T.sub.sat = 0.00053204591P.sup.3 - 0.07027440492P.sup.2 + 4.2630221429P - 98.92133288 Temperature Range 0° F. to 50° F. T.sub.sat = 0.000031298402P.sup.3 - 0.01112645218P.sup.2 + 1.8907849084P - 66.2388444 For refrigerant R-12 Temperature Range -10 to +50° F. T = 0.00025752709P.sup.3 - 0.04544987P.sup.2 + 3.7152263P - 66.375648 For refrigerant R-22 Temperature Range -10 to +50° F. T = 0.00006161138P.sup.3 - 0.017536207P.sup.2 + 2.3158884P ______________________________________ - 67.003218

Claim 39

A refrigeration system according to claim 32 wherein temperature T sh is set to be a minimum of approximately 5° F.

Claim 40

A refrigeration system according to claim 32 further comprising third temperature sensing means arranged adjacent the inlet end of said evaporator coil for sensing the temperature (T 3 ) of the refrigerant flowing into said evaporator coil and wherein said control means provides an output control signal for controlling operation of the refrigeration system for maintaining temperature T 2 greater than temperature T 3 .

Claim 41

A refrigeration system according to claim 35 wherein said control means provides an output signal for controlling the operation of the refrigeration system for maintaining temperature T 2 greater than temperature T 3 by an amount sufficient to insure that all of the liquid refrigerant passing through the evaporator coil is completely transformed into a gaseous refrigerant by the time that it is discharged from said evaporator coil.