U.S. patent application number 10/278418 was filed with the patent office on 2004-04-29 for heat treat hot gas system.
Invention is credited to Bischel, Kevin, McNamee, Peter, Moshier, Kenneth, Newton, Robert K., Singletary, Martin.
Application Number | 20040079095 10/278418 |
Document ID | / |
Family ID | 32106544 |
Filed Date | 2004-04-29 |
United States Patent
Application |
20040079095 |
Kind Code |
A1 |
Bischel, Kevin ; et
al. |
April 29, 2004 |
HEAT TREAT HOT GAS SYSTEM
Abstract
A hot gas heat treat system is employed to cool mix in a hopper
and a freezing cylinder and to heat the mix for pasteurization. A
hopper liquid line solenoid valve at the inlet of the hopper and a
cylinder liquid line solenoid valve at the inlet of the freezing
cylinder each control the flow of refrigerant to the expansion
valves which further control the flow of refrigerant that flows
around the hopper and the freezing cylinder, respectively. A hopper
hot gas solenoid valve at the inlet of the hopper and a cylinder
hot gas solenoid valve at the inlet of the freezing cylinder
control the flow of refrigerant from the compressor that flows
around the hopper and the freezing cylinder. The system further
includes a hot gas bypass valve that is opened when only the hopper
is being cooled to provide additional load to the compressor. An
EPR valve is positioned proximate to the hopper discharge to vary
the temperature of the refrigerant exchanging heat with the hopper.
A CPR valve is employed to control the inlet pressure of the
compressor by reducing the amount of hot refrigerant flowing into
the compressor suction. The system further includes a TREV valve to
allow for liquid refrigerant injection to the compressor suction to
control excessive compressor discharge during the cool cycle.
Inventors: |
Bischel, Kevin; (Rockton,
IL) ; Moshier, Kenneth; (Roscoe, IL) ;
Singletary, Martin; (Beloit, WI) ; Newton, Robert
K.; (Beloit, WI) ; McNamee, Peter; (Beloit,
WI) |
Correspondence
Address: |
CARLSON, GASKEY & OLDS, P.C.
400 WEST MAPLE ROAD
SUITE 350
BIRMINGHAM
MI
48009
US
|
Family ID: |
32106544 |
Appl. No.: |
10/278418 |
Filed: |
October 23, 2002 |
Current U.S.
Class: |
62/196.4 ;
62/238.6 |
Current CPC
Class: |
F25B 47/022 20130101;
A23G 9/08 20130101; F25B 2600/0272 20130101; A23G 9/228 20130101;
F25B 5/02 20130101; F25B 2600/2513 20130101; F25B 41/22 20210101;
A23G 9/225 20130101; F25B 40/00 20130101; A23G 9/163 20130101; A23G
9/222 20130101; F25B 41/20 20210101; F25B 2600/2501 20130101 |
Class at
Publication: |
062/196.4 ;
062/238.6 |
International
Class: |
F25B 041/00; F25B
049/00; F25B 027/00 |
Claims
What is claimed is:
1. A refrigeration system comprising: a compression device having a
compressor suction and a compressor discharge to compress a
refrigerant to a high pressure; a heat rejecting heat exchanger for
cooling said refrigerant; a hopper expansion device for reducing a
hopper portion of said refrigerant to a hopper low pressure; a
cylinder expansion device for reducing a cylinder portion of said
refrigerant to a cylinder low pressure; a hopper liquid line
solenoid valve positioned between said hopper expansion device and
said heat rejecting heat exchanger; a cylinder liquid line solenoid
valve positioned between said cylinder expansion device and said
heat rejecting heat exchanger; a hopper heat exchanger, said
refrigerant from said hopper expansion device exchanging heat with
a hopper mix in said hopper heat exchanger; and a cylinder heat
exchanger, said refrigerant from said cylinder expansion device
exchanging heat with a cylinder mix in said cylinder heat
exchanger.
2. The system as recited in claim 1 wherein said cylinder expansion
device is an AXV expansion valve.
3. The system as recited in claim 1 wherein said hopper expansion
device is a TXV expansion device.
4. The system as recited in claim 1 further a cylinder hot gas
solenoid valve positioned between said compressor discharge and
said cylinder heat exchanger and a hopper hot gas solenoid valve
positioned between said compressor discharge and said hopper heat
exchanger.
5. The system as recited in claim 4 wherein said cylinder liquid
line solenoid valve and said hopper liquid line solenoid valve are
opened and said cylinder hot gas solenoid valve and said hopper hot
gas solenoid valve are closed to allow refrigerant from said heat
rejecting heat exchanger to cool said hopper mix and said cylinder
mix.
6. The system as recited in claim 4 wherein said cylinder liquid
line solenoid valve and said hopper liquid line solenoid valve are
closed and said cylinder hot gas solenoid valve and said hopper hot
gas solenoid valve are opened to allow refrigerant from said
compressor to heat said hopper mix and said cylinder mix.
7. The system as recited in claim 6 wherein said hopper mix and
said cylinder mix are heated to above 150.degree. F. for at least
30 minutes.
8. The system as recited in claim 4 further including a hot gas
bypass valve positioned between said compressor discharge and said
compressor suction, and said hot gas bypass valve is opened to
increase said refrigerant flow to said compressor suction when said
hopper liquid line solenoid valve is opened, said cylinder liquid
line solenoid valve is closed, said hopper hot gas solenoid valve
is closed, and said cylinder hot gas solenoid valve is closed.
9. The system as recited in claim 8 further including a hot gas
bypass solenoid valve installed in series with said hot gas bypass
valve and activated in parallel with said hopper liquid line
solenoid valve, said hot gas bypass solenoid valve is opened when
said hopper liquid line solenoid valve is opened.
10. The system as recited in claim 4 further including a suction
solenoid valve positioned proximate to a cylinder heat exchanger
discharge, said suction solenoid valve is opened when said cylinder
liquid line solenoid valve is opened, and said suction solenoid
valve is closed when said system is off to prevent refrigerant from
migrating towards said cylinder heat exchanger.
11. The system as recited in claim 4 further including a suction
solenoid valve positioned proximate to a cylinder heat exchanger
discharge, said suction solenoid valve is opened at a same time as
said hopper hot gas solenoid valve is opened, and said cylinder hot
gas solenoid valve is opened after said suction solenoid valve and
said hopper hot gas solenoid valve is opened.
12. The system as recited in claim 1 further including an EPR valve
positioned proximate to a hopper heat exchanger discharge, said EPR
valve closing to increase pressure of said refrigerant in said
hopper heat exchanger and to increase temperature of said
refrigerant in said hopper heat exchanger.
13. The system as recited in claim 12 wherein said refrigerant in
said hopper heat exchanger is heated to 22.degree. to 24.degree.
F.
14. The system as recited in claim 1 further including a CPR valve
positioned proximate to said compressor suction, and said CPR valve
is restricted to reduce a suction pressure of refrigerant flowing
into said compressor suction, and to reduce a discharge pressure of
said refrigerant exiting said compressor discharge.
15. The system as recited in claim 1 further including a TREV valve
positioned between said heat rejecting heat exchanger and said
compressor suction.
16. The system as recited in claim 15 wherein said TREV valve is
opened to allow said refrigerant from said heat rejecting heat
exchanger to enter said compressor suction when a TREV sensor
senses that a compressor discharge temperature is 230.degree.
F.
17. The system as recited in claim 15 further including a CPR valve
positioned proximate to said compressor suction to reduce a
discharge pressure of said refrigerant exiting said compressor
discharge and a subcooler which exchanges heat between said
refrigerant from said heat rejecting heat exchanger and said
refrigerant entering said compressor suction, and said TREV valve
injects said refrigerant after said CPR valve and before said
subcooler.
18. The system as recited in claim 1 further including a cylinder
temperature sensor which senses a cylinder temperature of said
cylinder mix and a hopper temperature sensor which senses a hopper
temperature of said hopper mix.
19. The system as recited in claim 18 wherein said hopper liquid
line solenoid valve is opened when said hopper temperature sensor
detects said hopper temperature is greater than 39.degree. F.
20. The system as recited in claim 18 wherein said hopper liquid
line solenoid valve is closed when said hopper temperature sensor
detects said hopper temperature is less than 37.degree. F.
21. The system as recited in claim 1 wherein said hopper heat
exchanger is a hopper heat accepting heat exchanger and said
cylinder heat exchanger is a cylinder heat accepting heat exchanger
in a cooling mode, and said hopper heat exchanger is a hopper heat
rejecting heat exchanger and said cylinder heat exchanger is a
cylinder heat rejecting heat exchanger in a heating mode.
22. A refrigeration system comprising: a compression device having
a compressor suction and a compressor discharge to compress a
refrigerant to a high pressure; a heat rejecting heat exchanger for
cooling said refrigerant; a hopper expansion device for reducing a
hopper portion of said refrigerant to a hopper low pressure; a
cylinder expansion device for reducing a cylinder portion of said
refrigerant to a cylinder low pressure; a hopper heat exchanger,
said refrigerant from said hopper expansion device exchanging heat
with a hopper mix in said hopper heat exchanger; a cylinder heat
exchanger, said refrigerant from said cylinder expansion device
exchanging heat with a cylinder mix in said cylinder heat
exchanger; a cylinder liquid line solenoid valve positioned between
said cylinder expansion device and said heat rejecting heat
exchanger; a hopper liquid line solenoid valve positioned between
said hopper expansion device and said heat rejecting heat
exchanger; a cylinder hot gas solenoid valve positioned between
said compressor discharge and said cylinder heat exchanger; and a
hopper hot gas solenoid valve positioned between said compressor
discharge and said hopper heat exchanger, wherein said cylinder
liquid line solenoid valve and said hopper liquid line solenoid
valve are opened and said cylinder hot gas solenoid valve and said
hopper hot gas solenoid valve are closed to allow for cooling of
said hopper and said cylinder and said cylinder liquid line
solenoid valve and said hopper liquid line solenoid valve are
closed and said cylinder hot gas solenoid valve and said hopper hot
gas solenoid valve are opened to allow for heating of said hopper
and said cylinder.
Description
BACKGROUND OF THE INVENTION
[0001] A refrigeration system is employed to cool a mix in a frozen
dessert system. The frozen dessert system typically includes a
hopper which stores the mix and a freezing cylinder that cools and
mixes air into the mix prior to serving. The freezing cylinder is
cooled by a refrigeration system. Refrigerant is compressed in a
compressor to a high pressure and high enthalpy. The refrigerant
then flows through a condenser where the refrigerant rejects heat
and is cooled. The high pressure low enthalpy refrigerant is then
expanded to a low pressure. After expansion, the refrigerant flows
through the tubing encircling the freezing cylinder, accepting heat
from and cooling the freezing cylinder, and therefore the mix.
After cooling the freezing cylinder, the refrigerant is at a low
pressure and high enthalpy and returns to the compressor for
compression, completing the cycle.
[0002] The hopper is cooled by a separate glycol system that wraps
around the hopper and the freezing cylinder. The glycol that flows
around the freezing cylinder is cooled by the freezing cylinder.
The cooled glycol then flows around the hopper to cool the mix in
the hopper. To meet food safety standards, the mix in the hopper
must be kept below 41.degree. F.
[0003] The mix is also pasteurized every night to kill any
bacteria. The mix is heated for approximately 90 minutes to obtain
a temperature of at least 150.degree. F. The mix is kept over
150.degree. F. for 30 minutes, and then cooled back to 41.degree.
F. within 120 minutes. The mix is heated by heating the glycol with
an electrical heater. As the heated glycol flows around the hopper
and the freezing cylinder, the heat in the glycol is transferred to
the freezing cylinder and the hopper, warming the mix.
[0004] A drawback to this system is that both the freezing cylinder
and the hopper are coupled by the glycol system. During cooling,
when the cooled glycol flows around and exchanges heat with the
hopper, the glycol is heated by the hopper. When the glycol later
flows around the freezing cylinder again, the heat in the glycol
heats the freezing cylinder, melting the mix in the freezing
cylinder.
[0005] Additionally, during heating, the glycol first flows around
and heats the freezing cylinder. As the glycol rejects heat to the
freezing cylinder, the glycol is cooled. When this glycol flows
around the hopper, it is less effective in heating the hopper as
the glycol has already been cooled by the freezing cylinder.
Therefore, it takes longer to heat the hopper, resulting in a long
pasteurization cycle which requires over three hours to complete.
As the pasteurization cycle changes the flavor of the mix, a longer
pasteurization cycle can affect the flavor of the frozen
dessert.
[0006] Hot gas heating systems have been used in the prior art, but
did not allow for individual control of the cooling of the hopper
and the cylinder. Therefore, both the hopper and cylinder were
cooled at the same time and could not be cooled separately. If only
one of the hopper and the freezing cylinder required cooling, the
other would have to be cooled as well. As the suction lines of the
hopper and the freezing cylinder of the prior art are also not
de-coupled, it is difficult to vary the pressure, and hence the
temperature, of the refrigerant in the hopper and the freezing
cylinder. To achieve the best dessert product quality, it is
desirable to have the refrigerant cooling the mix in the hopper be
at a different temperature and pressure than the refrigerant
freezing the mix in the freezing cylinder. Another drawback of the
prior art hot gas system is also that there is a low system
capacity as an undersized compressor is employed to attain
compressor reliability.
SUMMARY OF THE INVENTION
[0007] The hot gas heat treat system of the present invention
includes a hopper which stores mix for making a frozen product. The
mix flows from the hopper into a freezing cylinder for cooling and
mixing with air. The refrigerant is compressed in a compressor and
then cooled by a condenser and changes to a liquid. The refrigerant
is then split into two paths, one flowing to the freezing cylinder
and one flowing to the hopper. The refrigerant flowing to the
freezing cylinder is expanded to a low pressure by an AXV expansion
valve and then accepts heat from the freezing cylinder to cool the
mix in the freezing cylinder. The refrigerant flowing to the hopper
is expanded to a low pressure by a TXV expansion valve and then
accepts heat from the hopper to cool the mix in the hopper. The
refrigerant flowing to the hopper is between 22.degree. and
24.degree. F. to keep the mix in the hopper between 37.degree. and
39.degree. F. After cooling the freezing cylinder and the hopper,
the refrigerant is at a low pressure and high enthalpy and returns
to the compressor for compression.
[0008] A liquid line solenoid valve is positioned at the inlet of
each of the hopper and the freezing cylinder to control the flow of
cool high pressure liquid refrigerant from the condenser to the
hopper and the freezing cylinder. A hot gas solenoid valve is
positioned at each of the inlet of the hopper and the freezing
cylinder to control flow of hot gaseous refrigerant from the
compressor discharge to the hopper and the freezing cylinder. When
the system is in the cooling mode, the liquid line solenoid valves
are opened and the hot gas solenoid valves are closed to allow the
flow of high pressure liquid refrigerant to cool the mix in the
hopper and the freezing cylinder. When the system is in the heating
mode for nightly repasteurization, both the hot gas solenoid valves
are opened and the liquid line solenoid valves are closed to allow
the hot gaseous refrigerant to warm the mix in the hopper and the
freezing cylinder.
[0009] When only the hopper is being cooled, not enough load is
provided on the compressor, affecting compressor reliability. A hot
gas bypass valve is opened to allow refrigerant gas from the
compressor discharge to flow to the compressor suction to increase
compressor load. Preferably, a solenoid valve is employed in series
with the hot gas bypass valve to prevent leakage of refrigerant
through the hot gas bypass valve.
[0010] An EPR valve is positioned proximate to the hopper discharge
to maintain the evaporator pressure of the hopper, and therefore
the temperature of the refrigerant flowing through the hopper. A
CPR valve limits the inlet pressure of the compressor by reducing
the amount of refrigerant flowing into the compressor suction. A
solenoid valve proximate to the discharge of the freezing cylinder
is closed when the freezing cylinder is not being cooled to prevent
warm refrigerant from migrating around the freezing cylinder.
[0011] The system further includes a TREV valve to allow for liquid
refrigerant injection to the compressor suction to control
excessive compressor discharge during the cool cycle. When the
compressor discharge temperature approaches 230.degree. F., the
TREV valve is opened to allow the high pressure liquid refrigerant
from the condenser to flow into the compressor suction, cooling the
compressor suction and therefore the compressor discharge.
[0012] These and other features of the present invention will be
best understood from the following specification and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The various features and advantages of the invention will
become apparent to those skilled in the art from the following
detailed description of the currently preferred embodiment. The
drawing that accompany the detailed description can be briefly
described as follows:
[0014] FIG. 1 schematically illustrates a prior art heat treat
system employing glycol as the refrigerant; and
[0015] FIG. 2 schematically illustrates a the hot gas heat treat
system of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] FIG. 1 schematically illustrates the prior art heat treat
system. The system includes a hopper 24 which stores a mix and a
freezing cylinder 26 that cools and mixes air into the mix prior to
serving. The freezing cylinder 26 is cooled by a refrigeration
system 20. Refrigerant is compressed in a compressor 28 to a high
pressure and high enthalpy. The refrigerant then flows through a
condenser 30 where the refrigerant rejects heat and is cooled. The
high pressure low enthalpy refrigerant is then expanded to a low
pressure in an expansion device 32. After expansion, the
refrigerant flows through the tubing encircling the freezing
cylinder, accepting heat from and cooling the freezing cylinder 26,
and therefore the mix. After cooling the freezing cylinder 26, the
refrigerant is at a low pressure and high enthalpy and returns to
the compressor 28 for compression, completing the cycle.
[0017] The hopper 24 is cooled by a separate glycol system 34. A
pump 44 pumps the glycol through the glycol system 34. The glycol
from a glycol tank 36 enters the glycol system 34 and flows through
a refrigeration line 38 wrapped around the freezing cylinder 26 and
is cooled. The cooled glycol then flows around the refrigeration
line 40 around the hopper 24, cooling the mix in the hopper 24.
[0018] When the mix is to be pasteurized, a heater 42 heats the
glycol. The heated glycol first flows in the refrigeration line 38
wrapped around the freezing cylinder 26 and heats the mix in the
freezing cylinder 26, cooling the glycol. The cooled glycol then
flows in the refrigeration line 40 wrapped around the hopper 24 and
heat the mix in the hopper 24. The glycol is less effecting in
heating the hopper 24 as the glycol has already been cooled by the
freezing cylinder 26. Therefore, it takes longer to heat the hopper
24 and complete the heating process of the mix.
[0019] FIG. 2 schematically illustrates the hot gas heat treat
system 120 of the present invention. The system 120 includes a
hopper 122 which stores mix for making a frozen product. In one
example, the hopper 122 is a 20 quart hopper. The mix flows from
the hopper 122 into a freezing cylinder 124 for freezing and mixing
with air. In gravity fed systems, a standard air-mix feed tube is
used to meter the air into the freezing cylinder 124. In pump
systems, air is metered into the freezing cylinder 124 by a pump.
Preferably, the freezing cylinder 124 is a stainless steel freezing
cylinder. The frozen product is then dispensed for serving.
[0020] The hopper 122 and the freezing cylinder 124 are cooled by a
refrigeration system. Refrigerant flows through the closed circuit
system. In one example, the refrigerant is R404A. The hot gas
refrigerant is compressed in the compressor 126 to a high pressure
and high enthalpy. The refrigerant then flows through a condenser
128 where the refrigerant rejects heat and is cooled by a fan 130
driven by a motor 132. In one example, the condenser 128 is a three
row {fraction (5/16 )} inch tube and raised lanced fin condenser
128. The condenser 128 can also be a water cooled condenser or an
air cooled condenser. However, it is to be understood that other
types of condensers 128 can be employed. Due to the high
refrigeration loads during the heat cycle, the capacity of the
condenser 128 must be increased versus similar capacity non-heat
treat configurations. Additionally, the size of the compressor 126
and the size of the condenser 128 are balanced and related to each
other.
[0021] The high pressure low enthalpy refrigerant is then expanded.
Prior to expansion, the refrigerant flow path is split into two
paths 134 and 136. One path 134 leads to the freezing cylinder 124
and one path 136 leads to the hopper 122.
[0022] The refrigerant flowing through path 134 to cool the mix in
the freezing cylinder 124 passes through an expansion valve 138 and
is expanded to a low pressure. Preferably, the expansion valve 138
is an AXV expansion valve. An AXV expansion valve is an automatic
expansion valve that constantly regulates pressure to control the
evaporating pressure of the refrigerant flowing around the freezing
cylinder 124 at -15.degree. F., allowing for consistent product
quality. This is important as the mix in the freezing cylinder 124
is sensitive to the fixed evaporator temperature. The cooling of
the mix in the freezing cylinder 124 commonly takes less time than
the cooling of the mix in the hopper 122. Although an AXV expansion
valve has been described, it is to be understood that other types
of expansion valve can be employed.
[0023] After expansion, the refrigerant flows through the tubing
encircling the freezing cylinder 124, accepting heat from and
cooling the freezing cylinder 124, and therefore the mix. The
refrigerant exits the tubing around the freezing cylinder 124
through path 144. Although tubing has been described, it is to be
understood that the refrigerant can flow through a chamber that is
proximate to the freezing cylinder 124.
[0024] The refrigerant flowing through path 136 to cool the mix in
the hopper 122 passes through an expansion valve 140 and is
expanded to a low pressure. Preferably, the expansion valve 140 is
a TXV expansion valve. A TXV expansion valve, or thermal expansion
valve, has a higher capacity for heat removal. The refrigeration
capacity required to cool the hopper 122 varies and is proportional
to the mix level in the hopper 122. The TXV valve provides control
of the refrigerant massflow to the hopper 122 and maintains the set
amount of superheat to assure compressor 126 reliability.
[0025] After expansion, the refrigerant flows through tubing
encircling the hopper 122, accepting heat from and cooling the
hopper 122, and therefore the mix. In one example, the tubing
encircling the hopper 122 is a copper tube refrigeration line
wrapped around and soldered to the bottom and the walls of the
hopper 122 having a diameter of approximately {fraction (5/16)} of
an inch in diameter. However, other diameters of tubing can be
employed. The surface area of the refrigeration line soldered to
the bottom of the hopper 122 is preferably maximized. The
refrigerant that cools the mix in the hopper 122 is between
22.degree. and 24.degree. F., keeping the mix in the hopper 122
between 37.degree. and 39.degree. F., below the standard of
41.degree. F. The refrigerant exits the hopper 122 through path
142.
[0026] After cooling the freezing cylinder 124 and the hopper 122,
the refrigerant is at a low pressure and high enthalpy. The
refrigerant paths 142 and 144 merge and the refrigerant returns to
the compressor 126 for compression, completing the cycle.
[0027] The system 120 further includes a receiver 180 that stores
excess refrigerant and helps to control the variable amount of free
refrigerant in the system 120. A heat exchanger/sub-cooler 182 is
employed to exchange heat between the gaseous refrigerant from the
freezing cylinder 124 and the liquid refrigerant flowing to the
expansion valves 138 and 140 to further increase capacity. The heat
exchanger/sub-cooler 182 is employed to warm the suction gas into
the compressor 126, ensuring that only gaseous refrigerant, and not
liquid refrigerant, enters the compressor 126, increasing
compressor 126 life. A filter/dryer 184 is employed to trap any
debris in the refrigerant and to remove any water which may have
leaked into the refrigerant.
[0028] The system 120 further includes two liquid line solenoid
valves 146 and 148. The liquid line solenoid valve 146 controls the
flow of cool refrigerant from the condenser 128 and to the freezing
cylinder 124, and the liquid line solenoid valve 148 controls the
flow of cool refrigerant from the condenser 128 and to the hopper
122. When the system is in cooling mode and both the freezing
cylinder 124 and the hopper 122 are cooled, both the liquid line
solenoid valves 146 and 148 are opened to allow the cooled
refrigerant to flow around freezing cylinder 124 and the hopper
122. During cooling, the hot gas solenoid valves 150 and 152
(explained below) are closed.
[0029] When the heat cycle is begun for pasteurization, the liquid
line solenoid valves 146 and 148 are closed, preventing cooled
refrigerant from flowing to the hopper 122 and the freezing
cylinder 124. The system 120 further includes two hot gas solenoid
valves 150 and 152. The hot gas solenoid valve 150 is positioned
between the compressor discharge 158 and the freezing cylinder 124,
and the hot gas solenoid valve 152 is positioned between the
compressor discharge 158 and the hopper 122. When the mix is to be
heated, the two hot gas solenoid valves 150 and 152 are opened to
allow hot gas from the compressor discharge 158 to flow around the
freezing cylinder 124 and the freezing cylinder 122 bypassing the
condenser 128. When the system is in heating mode and both the
freezing cylinder 124 and the hopper 122 are heated, both the
liquid line solenoid valves 146 and 148 are closed.
[0030] The mix is heated to at least 150.degree. F. for at least 30
minutes every night to repasteurize the mix and kill any bacteria.
As the refrigeration line is soldered to both the bottom and the
walls of the hopper 122, baking of the mix on the hopper 122 walls
is reduced as the heat is transferred to a larger surface area of
the hopper 122. Baking of the mix is caused by a mix film foam that
clings to the walls of the hopper 122 as the mix level drops. As
the hopper 122 and the freezing cylinder 124 are heated separately,
the mix can be cooled faster and the mix can be heated to
150.degree. faster, reducing the time of the pasteurization cycle
and therefore reduce the disfavoring of mix.
[0031] During the heating mode, it may be preferable to open the
hot gas solenoid valve 152 to heat the hopper 122 alone for a few
minutes prior to the opening of the hot gas solenoid valve 150 and
heating the freezing cylinder 124 to prevent compressor 126 flood
back. Each hot gas solenoid valve 150 and 152 is de-energized
asynchronously so that the valves 150 and 152 are controlled
separately. Temperature feedback is provided from both the hopper
122 and the freezing cylinder 124 by temperature sensors 174 and
172, respectively, to indicate when the mix has reached the desired
temperature. The temperatures of the mix in the hopper 122 and the
freezing cylinder 124 are provided to a control (not shown) which
controls the system 120.
[0032] The liquid line solenoid valves 146 and 148 and the hot gas
solenoid valves 150 and 152 are controlled separately by a control
186. Therefore, during cooling, the hopper 122 and the freezing
cylinder 124 can be separately cooled and during heat, the hopper
122 and the freezing cylinder 124 can be separately heated.
[0033] When only the hopper 122 is being cooled during the cooling
mode, the cooling of the hopper 122 alone may not provide enough
load on the compressor 126 and the compressor 126 suction pressure
droops, affecting compressor reliability. When only the hopper 122
is being cooled, the liquid line solenoid valve 146 leading to the
freezing cylinder 124 is closed, and the liquid line solenoid valve
148 leading to the hopper 122 is opened. A hot gas bypass valve 154
may open to allow hot refrigerant from the compressor discharge 158
to flow into the compressor suction 160, applying extra load to the
compressor 126 when only the hopper 122 is being cooled. The hot
gas bypass valve 154 is self-regulated. The refrigerant gas is
diverted from performing any refrigerant effect, but provides a
load to the compressor 126 to maintain the compressor 126 suction
pressure above 15 psig.
[0034] At all other times, the hot gas bypass valve 154 is closed.
However, it is possible that the hot gas bypass valve 154 may not
completely close, resulting in an undesirable leak of refrigerant
into the system 120. In one example, a hot gas bypass solenoid
valve 156 is employed in series with the hot gas bypass valve 154
to prevent the undesirable leakage of refrigerant from the
compressor discharge 158 into the system 120. The hot gas bypass
solenoid valve 156 is activated in parallel with the liquid line
solenoid valve 148 so that the solenoid valve 156 only opens when
the liquid line solenoid valve 148 is opened. However, it is to be
understood that the hot gas bypass solenoid valve 156 can be
activated by the control 186. When the control 186 determines that
the liquid line solenoid valve 148 for the hopper 122 is opened and
the liquid line solenoid valve 146 for the freezing cylinder 124 is
closed, indicating that the hopper 122 alone is being cooled, the
hot gas bypass solenoid valve 156 is also opened with the hot gas
bypass valve 154 to provide additional load on the compressor 126.
At all other times, the hot gas bypass solenoid valve 156 is
closed, preventing the leakage of refrigerant from the compressor
126 discharge into the system 120. It is to be understood that the
hot gas bypass valve 154 and the hot gas bypass solenoid valve 156
can be employed either alone or together.
[0035] The system 120 further includes an evaporator pressure
regulator valve, or an EPR valve 162, positioned proximate to the
discharge of the hopper 122. The EPR valve 162 is self-regulated.
As the refrigerant exchanging heat with the hopper 122 and the
freezing cylinder 124 both originate from the compressor 126, the
temperature of the refrigerant is set by the suction pressure of
the compressor 126 and is not adjustable. However, the refrigerant
flowing around the hopper 122 needs to be between 22.degree. to
24.degree. F. to cool the mix in the hopper 122 to 37.degree. to
39.degree. F., and the refrigerant flowing around the freezing
cylinder 124 needs to be about -15.degree. F. to cool the mix in
the freezing cylinder 124 to 20.degree. F. The EPR valve 162 is
employed to maintain the pressure of the refrigerant exchanging
heat with the hopper 122 at 60 psig. As the pressure of the
refrigerant exchanging heat with the hopper 122 is maintained at 60
psig, the temperature of the refrigerant flowing around the hopper
122 is maintained at a desired temperature. Preferably, the
refrigerant flowing around the hopper 122 is maintained between
22.degree. to 24.degree. F.
[0036] A crankcase pressure regulator valve, or CPR valve 164, is
employed to control the inlet pressure of the compressor 126 and to
maintain the compressor suction pressure below 40 psig. The CPR
valve 164 is also self-regulated. If the compressor suction
pressure increased above 40 psig, the compressor 126 can stall.
When the CPR valve 164 is throttled or restricted, the amount of
hot refrigerant flowing into the compressor suction 160 is
decreased. By decreasing the pressure of the refrigerant flowing
into the compressor suction 160, the pressure of the refrigerant
flowing through the compressor discharge 158 is also decreased.
Alternately, the CPR valve 164 can be eliminated if the orifices in
the hot gas solenoid valves 150 and 152 are sized to adequately
limit refrigeration flow. In this example, the TXV expansion valve
140 is a pressuring limiting TXV expansion valve 140 that regulates
the suction pressure of the hopper 122 to regulate the superheat
out of the hopper 122.
[0037] The system 120 further includes a temperature responsive
expansion valve, or a TREV valve 166, to adjust liquid refrigerant
injection to the compressor suction 160 to control excessive
compressor discharge during the cool cycle. The TREV valve 166 is
also self-regulating. A TREV bulb 168 positioned proximate to the
compressor discharge 158 to sense the temperature of the compressor
discharge 158. In one example, the TREV valve 166 and the TREV bulb
168 are connected by a capillary tube. When the TREV bulb 168
detects that the discharge temperature approaches 230.degree. F.,
the TREV valve 166 is opened to allow the cool high pressure liquid
refrigerant from the condenser 128 to flow into the compressor
suction 160, cooling the compressor suction 160 and therefore the
compressor discharge 158. Therefore, the compressor 126 discharge
temperature can be kept below than 250.degree. F.
[0038] A suction solenoid valve 170 proximate to the discharge 188
of the freezing cylinder 124 prevents refrigerant from migrating to
the freezing cylinder 124. When the system 120 and the compressor
126 is off, refrigerant tends to migrate to the freezing cylinder
124, which is the coolest part of the system 120, and heat the
freezing cylinder 124. When the freezing cylinder 124 is being
cooled, the suction solenoid valve 170 is opened to allow
refrigerant to discharge from the freezing cylinder 124. By closing
this valve 170 when the system 120 is off, the refrigerant is
prevented from migrating to and heating the freezing cylinder
124.
[0039] During heating, the hot gas solenoid valve 152 is first
opened to heat the hopper 122 first. Then hot gas solenoid valve
150 is then opened to heat the freezing cylinder 124. The suction
solenoid valve 170 is opened at the same time the hot gas solenoid
valve 152 is opened to allow any refrigerant in the freezing
cylinder 124 to boil off, preventing the refrigerant from flowing
to and slugging the compressor 126. Alternately, the hot gas
solenoid valves 150 and 152 and the suction solenoid valves 170 are
opened at the same time.
[0040] Temperature sensors 172 and 174 monitor the temperature of
the freezing cylinder 124 and the hopper 122, respectively. When
the system 120 is off and the temperature sensor 174 senses that
the temperature of the mix in the hopper 122 is greater than
39.degree. F., the system 120 is turned on and begins the cooling
mode to cool the mix in the hopper to 37.degree. F. The freezing
cylinder 124 further includes a beater 176. As the temperature of
the mix proximate to the door of the freezing cylinder 124 is
greatest, the beater 176 is turned on to stir the mix in the
freezing cylinder 124 and mix the product to equalize the product
temperature. An agitator 178 also mixes the mix in the hopper 122.
The agitator 178 is an auto stepping motor assembly mounted to the
bottom of the hopper 122 and turns a direct driven blade suspended
in the mix.
[0041] If the system 120 is turned on to cool the mix in the
freezing cylinder 124, the temperature of the mix in the hopper 122
is checked by the temperature sensor 174 prior to shutting the
compressor 126 off. If the temperature of the mix in the hopper 122
is detected to be greater than 37.degree. F., the cool refrigerant
is sent to the hopper 122 for cooling. Although the temperature of
the mix in the hopper 122 has not reached the threshold value of
39.degree. which triggers cooling, the hopper 122 is cooled at this
time as it is more efficient to cool the hopper 122 while the
system 120 is already operating in cooling mode.
[0042] The liquid line solenoid valves 146 and 148, the two hot gas
solenoid valves 150 and 152, and the suction solenoid valve 170 are
all controlled by the control 186, which is the main control 186 of
the system 120. The hot gas bypass valve 154, the hot gas bypass
solenoid valve 156, the EPR valve 162, the CPR valve 164, and the
TREV valves 166, are all self-regulated. When the control 186
detects that cooling of the hopper 122 and the freezing cylinder
124 is necessary, the control 186 turns on the system 120 and opens
the liquid line valves 146 and 148 to cool the mix in the hopper
122 and the freeing cylinder 124. The hopper 122 and the freezing
cylinder 124 can be separately cooled depending on system 120
requirements. When the control 186 detects that heat of the hopper
122 and the freezing cylinder 124 is necessary, the control 186
turns on the system 120 and opens the hot gas valves 150 and 152 to
heat the mix in the hopper 122 and the freeing cylinder 124. The
hopper 122 and the freezing cylinder 124 can be separately heated
depending on system 120 requirements.
[0043] When the system 120 is in auto mode, the cooling mode is
operated as needed when detected by the control 186 to maintain the
temperature of the mix in the hopper 122 and the freezing cylinder
122 within the desired ranges. When no frozen product is being
drawn from the freezing cylinder 124, the system 120 may be placed
in a standby mode. The system 120 enters the stand-by mode either
manually or at a programmed time. When the standby mode is
activated, the product in the freezing cylinder 124 is allowed to
melt. The mix in the freezing cylinder 124 is warmed to the
temperature of the mix in the hopper 122, reducing the amount of
churning which can ruin the product quality. When frozen product is
being drawn from the freezing cylinder 124, a switch is activated
and refrigerant is immediately sent to the freezing cylinder
124.
[0044] Although an AXV expansion valve 138 and the liquid line
solenoid valve 146 have been illustrated and described as expanding
and controlling the flow of refrigerant into the inlet of the
freezing cylinder 124, other devices can be employed. For example,
a stepper driven expansion device can employed, eliminating the
liquid line solenoid valve. The stepper driven expansion device can
be operated as either an AXV (by adding a pressure transducer to
monitor freezing cylinder pressure) or a TXV (by adding a
temperature transducer to the temperature outlet) by adjusting
refrigerant flow as a function of freezing cylinder pressure or
freezing cylinder superheat.
[0045] Although one system 120 has been illustrated and described,
it is to be understood that more than one system 120 can be
employed for different products. For example, two different systems
120 can be employed for two different products, such as soft serve
ice cream and shakes. Alternately, multiple flavors of a single
type of frozen product can bee employed in a single system 120.
Each flavor would utilized a separate hopper 122 and freezer
cylinder 124, but would share a compressor 126.
[0046] The foregoing description is only exemplary of the
principles of the invention. Many modifications and variations of
the present invention are possible in light of the above teachings.
The preferred embodiments of this invention have been disclosed,
however, so that one of ordinary skill in the art would recognize
that certain modifications would come within the scope of this
invention. It is, therefore, to be understood that within the scope
of the appended claims, the invention may be practiced otherwise
than as specifically described. For that reason the following
claims should be studied to determine the true scope and content of
this invention.
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