US1782651A - Refrigerating system - Google Patents

Description

Nov. 25, 1930.

J. F. HOFFMAN REFRIGERATING SYSTEM Filed March 7, 1927 2 She ets-Sheet l Nav. 25,` 1930. J. F. HOFFMAN REFRIGERA'IINGv SYSTEM Filed March 7. 1927 2 Sheets-Sheet 2 Patented Nov. 25, 1930 UNITED STATES PATENTy OFFICE JoHN s. HOFFMAN,` oFoMAKA, NEBRASKA, AssIoNonro BAKER, ICE MACHINE co.

INC., or OMAHA, NEBRASKA, A CORPORATION or NEBRASKA l REFRIGERATING SYSTEM AApplication aiednarch 7, 1927. serial No. 173,440.

My invention' relates to refrigerating systems andmore particularly to, one o that class employing ammonia as a refrigeration medium and includingl a plurality of units for refrigeration in separate compartments wherein different temperatures are to be maintained substantially constant.

It is a principal object of my invention to individually control the units inthe separate compartments whereby refrigerant may be suppliedto each independently of the other and to automatically connect and disconnect the units with the source of supply in accordance with the temperature condi- 'tions in such compartments. It is a further object of my invention to eliminate reverse cycling of the refrigerant from a unit in a compartment of higher temperature to those units in compartments of4 lower temperature through the low pressure line.

It is a further object of my invention to effect defrostin of the refrigerating units by reverse cyclmg of the refrigerating medium.

' In accomplishing these and other objects of the invention l have provided a system and apparatus, the preferred form of which is illustrated in the accompanying drawings,

3o wherein i y Fig. 1 is a diagrammatic view of a refrigerating system embodying my invention,

illustrating the 'systemes includinglthree separate cooling compartments with their re-l the thermostatically controlled discl'narge controlled from the system, be described. y A

Leading from the compressor 1 is a pri mary condenser 2 and a receiver 3,-both of ordinary construction. Leadin from the reas Will presently ceiver 3 is a line 4 for con ucting liquid refrlgerant to the various compartments served by the system and which may be tapped to supply an indirect refrigerating coil indicated by the tank 5, and which will be more specifically referred to' following the description of the direct refrigeration.

The compartments numbered 6, 7 and 8 may be insulated compartments commonly found in cold storage warehouses or the like and here shown to be three in number for illustrative purposes without intention of limiting capacity of the system, .and for fur-l ther illustration it will be assumed that the temperature of the compartment 6 is to be 70 maintained at about 38 F., the compartment 7 at about 20 F., and the compartment 8 at about 5 F.

As the mechanical construction of the refrigerating unit in each of the compartments isidentical With those in the other compartments, but one Will be referred to with the understanding that description of it applies equally to each of the others.

Leading from the line 4f within the com- 30` partment 6 is a branch supply line 9, opening to the bottom of a cooling coil 10 througha primar unit control valve mechanism, designate generally by 11 and hereinafter more specificallydescribed. Leaving the coil 10 at the top is an outlet branch line 12, passing through a thermostat condenser jacket 13, containing gas, preferably and hereinafter referred to as ammonia gas, 14 whereby the primary control valve mechanism is iniiuenced for the purposes presently mentioned. Leaving the jacket 13 the line 12 passes into the casing 15 of the remote control back pressure valve mechanism, indicated general, ly b the numeral 15, and leaving said valve mec anism to enter the return or low pres sure line 16 whereby the refrigerating agent is returned to the compressor through a suction line 17 When the system has been in operation for till a sucient period to reduce the temperature lof a compartment to the desired degree indicated by the setting of a thermostat within the compartment, it is necessary or desirable to interrupt flow of refrigerating agent to the cooling coil in such compartment in order to prevent accumulation of an excess of the agent within the coil. This interruption of supply is eii'ected primarily at the valve mechanism 15 at the outlet of the coil. Continued supply of the refrigerant to the opposite end of the coil builds up a pressure withy by suitable bolts 24 and its inner face chambered to form the upper part of the idiaphragm chamber 22.

p Extending across the diaphragm chamber with its periphery clamped between the flanges of the body fitting and cap is a flexible diaphragm 25, held securely within the valve case'by the bolts 24' which secure the cap to the casing 5. Bearing against the under face or the diaphragm 25 is a reinforcing plate 26 carried by a valve stem 2'? which extends through 'the bore 28 in the nipple 21 and carries a valve head 29 tapered to lit within the valve seat 30 in the lower end of the nipple 21. y

The vertical chamber 20 is closed at its lower end by a screw cap 31 and seated on said cap is a cylinder 32 containing a piston 33 urged against the valve head 29 by a s ring 34, which seats in the bottom of the cylinder and ltends 'to assist in closing the valve 29 against its seat to exclude reirigera'ting rnedium from the diaphragm chamber 22.

@pposing the spring 34 at the opposite side of Athe diaphragm is a spring 35, housed within dome on the cap seating at its lower end on a head 37 attached to the upper surface of 'the diaphragm having a retaining boss 38 about which the lower end oit-the spring is located to anchor the spring. .fat its upper ond the spring 35 bears against 39 on an adjusting screw 40, which is 'threaded into 'the top oi the cap dome 23 and whereby the 'tension of spring 35 is regulated predeterinine the bach Invest-:nre at 'which valve Win close the nne and shut the c. .Q l. P '.T L L lansler of. heat .from the compartment to be cooled to the refrigerating ag'ent during passage of the agent through the compartment; consequently, temperature of the agent f is higher upon leaving the compartment than upon enterind. ing coil as a saturated vapor and transfer of heat units from the compartment to the agent transforms this vapor into a drier, gaseous condition, which is more favorable for operationof the compressor. 'Should the agent pass through the compartment Without doing any useful work, it would leave the compartment in the same conditionat which it entered and in a condition unfavorable for compressor operation. Consequently, it is desirable to eliminate this condition when it may occur.

To effect this elimination I provide the line 9 between the back pressure valve. 18 and the cooling coil with a thermostatically controlled valve for diminishing the supply of refrigerating agent to the coil under the condition last above mentioned. This valve ispreferably of the construction illustrated in Fig. 8 and indicated generally by the numeral 42, which designates the valve casing. The part of the line leaving the back pressure valve 18 and designated 9 opens into a primary chamber 43 inthe valve casing 42, containing a scale trap 44, preferably of skeleton 'formation and screened at 45 to filter the refrigerating agent in its passage to the cooling coil. The trap 44 rests on the top of a plug 46 in the bottom of the housing and normally closing a cleanout opening .47.

Leading from the top of the chamber 43 is a Vtube 48 connecting 'the chamber 43 with a iitting 49, containing a valve (not shown) operable by a hand wheel 50 to control flow of refrigerating medium from the chamber through the hitting. The fitting communicates through a conduit 51 with the condenser jacket 13 in the outlet line from the cooling coil and carries an .indicator` 52 for disclosing the volume of content of the jacket. llt is through. this connection that the thermostatic 'duid is delivered to the condenser jacket under control of the valve indicated at 5G.

Communicating with the chamber 43 through a bore 53 is a chamber 54, which, in turn, communicates with a chamber 55, as will presently be described, and which charnber 55 communicates with the lower convolution ont' the coil il) through a bore Located within the chamber 54 is plate 5T having a central aperture 58. Located chamber 54 below the plate 57 is a head 59, comprising a depending boss 60, an opstanding boss 61 and an annular Aafiange 62,. Seated in the bott-onaof the chamber 54 about an opstanding boss 63 is a spring 64, supporting the bead 59 against hall 65 within 'the central. aperture 59 in the plate 5? and serving valve 'to control low of the rei igerating The agent enters the cooli agent from the chamber 54. The bore 66 has a seat 66 in the lower head 67 of'a nipple 68 that extends into the chamber 55 'and provided with a lateral ports 69 whereby liquid from the chamber54 is delivered from the nipple 68 into the chamber. 55.

Located within the bore of the nipple 68 is a square pin 70 which serves to hold the valve ball downwardly but does not inter' fere with flow of fluid through the nipple. The pin engages a plate 71 on the lower face of a diaphragm 72, held between the top.

of the valve housing 42 and the valve housing cap 73. The cap 73 comprises an upstanding cylindrical body 74, containing a spring-retaining cup 75 having limited vertical movement because of its iitting within a shouldered recess 76 Awithin the lower portion of the cylinder 74.

Seated within the cup is a coiledl spring 77, the upper end of which lits over a cap plug 78 within the upper portion of the cylinder. Extending through the cylinder is a 82 into which the refrigerating agent is delivered after its passage through the condenser jacket upon leaving the cooling coil.' 'The chamber 82 is formed at the bottom of the. casing 15 by a partition 83 having a port opening' 84 controlled by a late valve 85 havingv a stem 86 slidably tted within a socket-87 at the bottom of they casing and yieldingly urged to its seat by a spring 88 seated within the socket and bearing against the lower end of the valve stem.

Extending from the top of the valve plate is a shank 89, carrying a disk 90 which bears against the under face of a flexible diaphragm 91, extending horizontally across the upper valve chamber' 92 with its periphery locatedbetween a flange 93 on the body of the valve casing and a flange 94 on the cap member 95; bolts 96 extendinfr vthrough the flanges and throughthe diapragm to securely connect the parts together.

On the upper face of the diaphragm is a head 97 lhaving a boss 98 forming an anchorelement to the coil `and that when the temperature rises, the element is movedr away from the coil to reduce the heating effect.

The thermostat tube 106 traps the return line from the coil 10 through a tube 111, through which the thermostat tube is supplied With fiuid from the return line, the tube 111 being controlled by a valve 112 so that when the coil 107 is filled, the connection may be broken. This connection is provided when the ammonia is employed as the thermostatic fluid but I do not wish to limit myself to this particular thermostatic agent.

'I he heating element 109 is energized from a` suitable source of electrical supply through lead lines 113-114 (Fig. 1) in circuit with a thermostatic switch 115 located withinaml subject to changes in temperature of the compartment containing the cooling coil 10-and also in f circuit with a manual switch 116, which may be located within the compartment under refrigeration or at any other convenient place. and 114- is an automatic switch 117 for controlling flow of current to the compressor motor so that the motor may be cut in and cut out automatically under influence of temperature within any of the compartments under refrigeration, the circuit also including an ordinary master switch 118.

The circuit heretofore described is duplicated in each of the other compartments under refrigeration, each compartment having its individual unit and individual automatic and manual controls, the only difference between the several units being that in those compartments wherein lower temperatures are desired, the coil is extended to provide greater i.

cooling surface. Each of the several units has its individual connection with the supply or high pressure line 4- an'd with the return or low pressure line 16.

I preferably also include Within the system an indirect cooling element; i. e., means for cooling brine which, in turn, is employed as a cooling agent for convenient sdistribution to other compartmentsv or any location requiring refrigeration or for the manufacture of ice. This indirect element of the system comprises a coil submerged in a brine tank 121, the coil being connected with the supply or high pressure line 4; through a branch 122 and with the return or low pressure line through a branch 123.

Located in the supply line 122 is a back pressure and thermostatically controlled valve mechanism corresponding to those previously described in connection with the direct cooling coil 10 and with a remote control valve mechanism, also corresponding to that in the direct cooling unit; the local thermostat controlling the last-named valve mechanism being of a type adapted for submergence in the brine in the tank 121 and con nected with the circuit 113-114, as are the Also included in the circuit 113 other corresponding thermostatic controlling elements.

It is well known in refrigeration practice that cooling coils of the type illustrated will frost; that is, will accumulate a condensation which adheres to the cooling surface and when the compartment under refrigeration is below the freezing point, will form frost, insulating the coils and interfering with the passage of the heat units from the compartment into the refrigerating Huid within the coil, thereby cutting down the efficiency of the unit. In order to overcome this disadvantage I provide for defrosting the coil by employing the hot liquid in the receiver at the compressor end of the system` for melting the frost and restoring the unit to its proper effectiveness.

In accomplishingthis result I provide the intake end of the coil 10 with a by-pass line 124, heretofore mentioned, for carrying fiuid about the back pressure and thermostatic supply valve 11, the by-pass having a manually operable valve for controlling the by-passiiow. As the defrosting operation is effective through proper control of the remote control valve mechanism as well as by by-passing the back pressure and thermostatic valve, no further mechanism is required, the operation being presently described in the description of use of the system.

Before installing a system embodying my improvements I first ascertain the capacity necessary for operating the system in order that a condenser of sufficient capacity to supply all of the units when operating at their full capacity may be provided.

Assuming installation of a system including three separate compartments in which the temperatures are to be held respectively at 38, 20o and 5 F., and that a compressor and condenser as well as unit coils of proper capacity are included in the system and that an indirect cooling unit is also included in the system, the operation is as follows:

Ammonia gas is compressed and condensed to liquid, which is accumulated in the receiver and at a temperature corresponding to the pressure at which it was compressed and which, we will assume, is 900 F., within the receiver.

rIhe back pressure valve in each of the units` is adjusted to permit free flow of the refrigerant to the units until a pressure has been built up in the unit sufficient to produce the desired temperature Within the compartment and the automatic temperature valve l12 in the supply connection to each unit is adjusted so that relatively high temperature at the discharge end of the unit, such as is present before the refrigerant is supplied to the unit, when expanded, will exert a pressure on the diaphragm 72, tending to open the valve and permit free ow to the unit.

of eachunit is adapted to close the connec-l tion between the unit and the return line under tensionv of the spring at the bottom of the valve which tension normally overbalances suction in the return line operating on the valved diaphragm in opposition to the spring.

Under these conditions when the system isplaced in opera-tion, refrigerant flows to the severalfunits in the system, passes the automatic back pressure and regulating Valve at the supply end of the unit, fills the coil,jand

is held in the coil because of the closure of' the valve at the discharge end of the unit.A

When the coil is filled and pressure is built up therein to the proper degree, back pressure in the coil operates the back pressure valve and cuts ofi' the supply of refrigerant.

because of the interruption of the cooling action of the coil. When the temperature has reached a sufficiently higlflimit, it acts on the thermostat 115 to close the electrical circuit to the heater, influencing the thermostat 107. When this circuit is closed, the heater is energized, the temperature of contents of the thermostat is raised anda pressure built up in the upper chamber of the control valve 15, opening that valve so that flow to the return line is established, relieving pressure in the coil so that fresh refrigerant may be delivered through the back pressure and regulating valve.

The cycle of refrigeration in the unit just described is then repeated until the temperatureof the compartmenthaslowered sufiiciently to effect a reverse operation of the thermostat 115, when the heater circuit is shut olf,`

contents of the thermostatic tube cools and the control valve 15 again closes to shut ofi' the outlet and again build u a pressure in the coil, as beforel described. T is operation continues automatically while the system is in use, the supply of refrigerant being regulatedat the back pressure valve to provide the proper amount of refrigeration for maintaining the compartment at the desired and predetermined temperature.

The operation described in connection with one unit is repeated in each of the other units, the only difference being in temperature which is determined by a setting of the individualback pressure valves.

It is apparent from the above that there will be a variation of ressure in the return line because of the di erent pressures under which the several units operate and the va` riable settings of the valves. As the compartments to be kept at the lower temperatures `must have a freer circulation of refrigerant low temperature units; consequently discharge from one ofthe high temperature units to the return line would tend to flow in thedirection of thelower temperature units and interfere with refrigeration in such units un- `less means were provided to prevent such unit, they-tend to expand the diaphragm 91 in the valve of such low temperature unit and consequently close-'the valve to prevent flow of such gases into the low temperature coil, thereby avoiding interference withy refrigerationtherein. Beingunableto escape into the low temperature coils, these gases are then conducted back to the compressor through the return line. Consequentlythe gases from any one of the units is not permitted to enter the coil of any of the other temperature units, the flow from the high temperature units being prevented by mechanical operation of the valves and iiow from a low temperature unit to a higher temperature Vunit being prevented by the higher pressures inthe higher temperature units, and all of the units may operate simultaneously at their dili'erent temperatures without interference one with another. It has heretofore been statedthat thevalves 15 controlling discharge from the units are setto normally close under tension of theirv springs and are opened automatically through the thermostat controlledby tern-l perature in the compartment served by the units. As more rapid refrigeration can be effected by a freev flow of the refrigerant through the coil, it is desirable to open thev discharge when the system is first placed in operation so that the refrigerant may flow freely through the coils to the return line. Inorder to effect this opening and quick cooling of the compartments, I provide for Ans master switch 118 and automatic switch 117,

the automatic switchin turn being under control of thev thermostats 115 in the several units. Consequently when the thermostatic switches 115 are open during such periods after the compartments served by the units are at proper temperature, current is cut olf from the motor and the compressor is idle. When, however, the temperature in the coin- Cell partments served by any one of the cooling units rises above the critical temperature and the therinostatic switch 115 is automatically operated, closing the valve 15, it acts on the switch 117 to close the circuit to the motor and the compressor is automatically started in operation.

The above describes the normal operation of the system.

The refrigerant, in those compartments held at a temperature above the freezing point, passing from the coil to the return line, is at a temperature below that of freezing, any moisture in the compartment served by the coil will settle on and frost the coil. Vhen the unit is automatically cut oil through the thermostatic control, the liquid in the coil in a compartment held at a temperature above the freezing point rises in temperature to approach temperature of the compartment and when it passes above the freezing point, tends to melt the frost and remove the frost incrustation.

As this automatic defrosting cannot ,take place in a compartment held below the fieezing point, I provide manually controlled means for effecting defrosting of such units. This manual control. includes the ley-pass about the back pressure and regulating valves at the intake end of each coil, together with the valve controlling discharge from the unit and which is normally under automatic control of the thermostat 115. When it is desired to defrost one of the low temperature coils, I open the by-pass about the back pressure and regulating valves at the intake end of the coil and open the circuit tothe electrical heater 109 so that the therin ostatic switch cannot effect opening of the discharge valve. With the unit set in this way, liquid from the receiver 3 is passed into the coil of the set unit and, being unable to pass' on to the return line, accumulates in the coil. Being unable to expand and perform its normal refrigerating function and having entered the coil at a temperature of approximately 90?", it is apparent that this high temperature acting on the incrustation on the coil will tend to melt the frost and clean the surface.

It is further apparent that transfer of heat from the ammonia during the frosting operation reduces temperature of the ammonia so, that when the defrosting has been conipleted, the temperature of the ammonia in the lower portion of the coil has been lowered to a degree which will render it eiective for refrigeration in the succeedingly lower temperature units in the system.

lle-frosting of any one of the units does not interfere with the normal operation of the other units as the opening of the circuit local at any of the units will not interfere nitii automatic opening` and closing of the circuit through the thermostatsat the other units.

It is apparent, therefore, that I have provided a refrigerating system wherein independent units served by the system may operate to maintain different temperatures in different compartments without interference one with the other, that such units are automatically controlled by local temperatures and that defrosting of the coils in higher temperature compartments is automatic and that in lower temperature compartments may be effected at will and without interference with the operation of any of the other units.

l/Vhat I claim and desire to secure by Letters Patent is:

1. In a refrigerating system, a cooling unit, valve mechanism controlling return flow from said unit, thermostatic means controlling said valve mechanism, and an electrical heater controlling said thermostatic means and automatically controlled by temperature of a compartment served by said unit.

2. In a refrigerating-system, a coolingi unit, valve mechanism controlling return flowfrom said unit, thermostatic means controlling said valve mechanism, an electrical heater controlling said thermostatic means and automatically controlled by temperature of a compartment served by said unit, and a manual switch in the heater circuit.

8. In a refrigerating system, a cooling unit having supply and discharge lines, valve mechanism controlling the supply line and controlled by temperature in the discharge line, a by-pass about said valve mechanism whereby the unit may be supplied independently of the suppl through the temperature controlled valve, tliermostatic means for con trolling the discharge line, normally inert means for heating said thermostatic means, and manually operable means controlling the heating means.

4. In a refrigerating system, supply and return lines, a cooling unit having connections with said. lines, an automatic valve in the return connection, normally tending lto close said connection, a thermostat comprising a container for expansible iiuid in coinmu'nication with the valve-whereby the valve is controlled by temperature of fluid in said container, a heater for the container. and connection between the container and heater whereby relation of the heater to the container is automatically varied according to temperature of contents of the container.

5. In a refrigerating system, in combination with supply and return lines, a cooling unit having its opposite ends connected with said lines, an automatic valve normally tending io obstruct discharge from said unit to the return line, a thermostat controlling said valve, an electrical heaterfor said thermostat and controlled thereby to vary heating relation of the lieaterto the thermostat according to temperature of the thermostat, a

thermostatic switch in the heater circuit con-l trolling the circuit by temperature in a compartment served by said unit, and a manual switch in said circuit. f

6. In a refrigerating system including a plurality of independent cooling units, each adapted for serving a separate compartment, and supply and return lines having branches to said units, independent means automatically controlling discharge from each unit by temperature of the compartment served by the unit, and means in each supply branch responsive to pressure inthe supply branch and to temperature of the related discharge branch automatically controlling supply of refrigerant to the units.

7. In a refrigerating system including a plurality of independent cooling units, each adapted for serving a separate compartment,

y and supply and return lines having branches to said units, independent means automatically controlling discharge from each unit by temperature of the compartment served by the unit, and means in each supply branch for controlling supply of refrigerant to the units including means responsive to pressure in the supply branch and means responsive to temperature of the discharge branch oit said unit.

In testimony WhereofI 'aflix my signature. JOHN F. HOFFMAN.

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