Air conditioning system

Sept. 6, 1938.

2,129,202

Μ. K. DREWRY

AIR CONDITIONING SYSTEM Filed Sept. 18, 1933

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Patented Sept. 6, 1938

2,129,202

UNITED STATES PATENT OFFICE

2,129,202

AIR CONDITIONING SYSTEM Montrose K. Drewry, Milwaukee, Wis. Application September 18, 1933, Serial No. 689,935

Claims.

This invention relates in general to air conditioning systems and particularly to apparatus for conditioning air and circulating it through enclosed spaces.

An object of the invention is to provide a simple and efficient air conditioning apparatus for regulating the temperature and humidity conditions of the air in a building.

Another object of the invention is to provide 10 an air conditioning system that is arranged to operate efficiently and with minimum attention.

Another object of the invention is to provide an air conditioning system having means for automatically regulating the rate of combustion 15 of fuel and the rate of circulation of air in accordance with conditions in the space being served with conditioned air.

A further object of the invention is to provide a new method of operating a heat exchange 20 system in which, while the system is used for cooling purposes, the boiler is operated to heat storage water and is at all times prepared to take on a heating load.

According to the present invention, air con25 ditioning apparatus having an air circulating system is provided with an air cleaner, a humidifier and a heat exchanger adapted to heat or cool the air as conditions may require. For heating the air, a boiler provided with an auto30 matic fuel feeding hopper is connected to the heat exchanger, and automatic means are provided for regulating the rate of combustion of fuel in the boiler and the rate of circulation of air in the circulating system in accordance with 35 temperature conditions in the space being heated.

Flue gases are drawn through the fuel in the hopper to condition it for feeding by gravity and to improve its qualities for combustion. In warm weather, cold water is circulated through 40 the heat exchanger to cool the air and to condense excess moisture out of it. Coincidentally, the boiler may be utilized for heating service water.

The foregoing and other objects of the inven45 tion may be achieved by the air conditioning system described by way of example in the following part of this specification in conjunction with the accompanying drawing, in which the single figure is a view, partly in side elevation 50 and partly in vertical section, of apparatus embodying the invention installed in the basement Of a building.

The illustrated air conditioning apparatus couprises, in general, an air circulating system 55 including a conditioning chamber or cabinet I (Cl. 257—3) of rectangular shape associated with a heating furnace or boiler 2. The air conditioning apparatus is preferably located in the basement of the building to be served and the conditioning chamber I may be supported conveniently from 5 the basement ceiling, as shown. Air to be conditioned is drawn from the rooms of the building being served into one or more intake registers 3 and through associated intake pipes or ducts 4 into the conditioning chamber I. 10

A partition 5, disposed in a vertical medial plane of the chamber I and extending from the top downward to near the bottom thereof, divides the chamber into an intake compartment 6, to the top of which the intake pipes 4 are 15 connected, and a discharge compartment 7. The partition 5 constrains the flow of the incoming air and directs 4t downward through a filter 8 arranged horizontally in the intake compartment 6 in position to remove dust and other 20 foreign particles from the air. From the filter, the air flows downward to the bottom of the compartment 6 and thence horizontally through a connecting passageway beneath the lower end of the partition S into the compartment 7. 2i

At the bottom of the compartment 7, there is arranged a humidifying tank or pan 9 that presents a surface of warm water to the inflowing filtered air from which the air absorbs a predetermined amount of moisture. 30

Above the humidifier 9, there is arranged a heat exchanging radiator 10 that functions to heat or cool the air, according to the requirements of weather conditions, as it flows upward in the compartment 7. From the top of the com- 35 partment 7, the air flows into outlet pipes 11 through which it is delivered to one or more discharge registers 12 in the rooms of the building being served, the air circulating system functioning, in general, in much the same manner 40 as the circulating system of the usual warm air furnace.

The heat exchanger 10 is of the fin-ahd-tube type, having an inlet manifold or header 13 which is connected by an inlet pipe 14 to the 45 upper part of the boiler 2 and from which a bank of finned tubes 15 extends horizontally across the compartment 7 to a return header 16. From the return header 16, a second bank of finned tubes 17 extends across the compartment 50 beneath the tubes 15 to a discharge header 18 which is connected by a return pipe 19 to the lower part of the boiler 2. The tubes 15 and IT are so spaced and positioned that the air, in flowing upward through the heat exchanger, gg

2,129,202 first passes between the tubes IT of the lower bank and then passes between the tubes 15 of the upper bank.

As shown In the drawing, the heat exchanger 5 10 is arranged substantially at the level of the top of the boiler 2 to facilitate the circulation of hot water from the boiler through the water circulating system. In cold weather, when the system is being used for heating the building, 10 hot water from the top of the boiler 2 flows horizontally through the inlet pipe 14 into and through the upper tubes 15 and then back through the lower tubes IT of the heat exchanger 10 in series relation, giving up a portion of its 15 heat to the air in the compartment T. The water then flows from the heat exchanger into the vertically arranged return pipe 19 and thence back to the bottom of the boiler.

As the column of relatively cool water in the 20 vertical return pipe 19 is heavier than the corresponding column of hot water in the boiler, it descends by gravity, causing circulation by natural convection or thermo-syphon action through the heat exchanger. Because the heat exchanger 25 is positioned substantially level with the top of the boiler, the column of cool water in the return pipe 19 is of sufficient height to cause effective thermo-syphon action in the system.

The air in the circulating system likewise is 30 caused to circulate by thermo-syphon action, the heated air in the compartment 1 rising into the outlet pipes I I and being replaced by cool air from the compartment 9. To effect circulation of the air by thermo-syphon action it is desirable 35 that the heat exchanger be placed as low as, possible in the air circulating system in order that the column of heated air may be of sufficient height to establish a difference in weight between it and the corresponding column of cold air great 40 enough to provide pressure for effective circulation. By positioning the heat exchanger at the level of the boiler top, the conditions necessary for thermo-syphon circulation of both the water and the air are met in manner to effect equally 45 satisfactory circulation of each.

The boiler 2 is provided at its top with an expansion tank or chamber 20 that serves as a storage reservoir for water which may be forced out of the boiler when the water therein is ex50 panded by heat. The tank 20, being open to the atmosphere, also permits the escape of air or steam that might otherwise interfere with the circulation of the water through the system, should the pipe 14 become air-bound or steam55 bound by reason of becoming filled with either fluid.

An adequate supply of water is automatically maintained in the boiler at all times by means or an inlet valve 21 that controls the inflow of 60 water from a supply pipe 22 to make up for water lost by evaporation or otherwise. The valve 21 is actuated automatically by a float 23 resting on the surface of the water in the expansion tank. The float 23 covers substantially all of the sur^{65 Iace th}e water in the tank and greatly reduces the absorption of air by the water when it cools below its boiling temperature, thereby avoiding corrosion of the interior of the water circulating system apparatus by air dissolved in the water.

Fuel for combustion in the firebox of the boiler 2 is fed into the firebox automatically by gravity from an air-tight fuel hopper 24 mounted on one side of the boiler. The hopper 24 may be filled periodically with solid fuel such as coal or coke 75 through an opening 25 in 'ts top which is normally closed by a close-fitting removable cover 20. The flue gases resulting from combustion of the fuel are conducted from the firebox by a smoke-pipe 2T that discharges into a chimney 28. _g

A relatively small pipe 29 is connected between the smoke-pipe 27 and the upper part of the fuel hopper 24 for conducting flue gases from the smoke-pipe into the top of the hopper to be drawn downward through the fuel by the natural 10 draft of the firebox to condition the fuel for feeding and burning. The flue gases passing through the hopper, together with heat conducted from the boiler to the hopper, act upon the fuel therein in such manner that water vapor and certain 15 gases are driven off and the fuel is otherwise so modified as to prevent burning or clogging thereof in the hopper or caking upon flowing from the hopper into the firebox. The conditioned fuel flows into the firebox by gravity continually and 20 automatically at the rate at which it is required to replace the fuel consumed, thus maintaining a uniform bed of burning fuel on the firebox grate at all times.

An opening 30 is provided in the side of the 25 firebox above the level of the fuel bed therein for introducing auxiliary air into the combustion chamber. To control the amount of auxiliary air introduced, the opening is provided with an adjustable cover 31. The opening 30 may be 30 utilized for starting the fire when the hopper contains a supply of fuel, as kindling materials may be inserted through it into the firebox and ignited. A further function of the opening- 39 flre° ^{observation of} the condition of the 35

The rate of combustion of fuel in the firebox and the rate of heating resulting therefrom is regulated by a thermostat 32 so located as to be responsive to the temperature of the air in the 4η rooms being heated and arranged to be regulated to maintain the air in the rooms at a predetermined desired temperature. The thermostat 32 is connected to a thermostat motor 33 in such manner as to energize it in response to changes ta the room temperature. The thermostat motor 33 is connected, by a continuous chain 34 carried by pulleys 35, to operate a draft door 36 arranged to control the admission of air into the firebox beneath the bed of fuel therein, and to operate a check door 37 arranged to control the admission of air into the base of the chimney 28 for checking the fire.

When the temperature of the air in the rooms being heated falls below the predetermined de- v sired temperature for which the thermostat is set, the thermostat and its associated motor function to close the chimney check door 37 and to open the draft door 36, thereby increasing the draft through the firebox and increasing the «η rate of combustion of fuel to furnish additional heat to the boiler water.

The boiler is provided with a water temperature regulator 38 that includes a thermoexpansion element 39 disposed in contact with 65 the water in the boiler and connected by a link 40 to a pivoted lever arm 41 on which is slidably mounted an adjustable counterpoise weight 42. As the temperature of the boiler water increases in response to the action of the thermostat 32, 70 the thermal expansion element 39 expands and pivots the lever arm 41, lifting the weight 42. When the water temperature reaches a predetermined value, the lever arm 41 is pivoted to such position that an electrical switch 43, pref- 75

2,129,202 steam which would otherwise interfere with the circulation of the water through the heat exchanger 10 by steam-binding the pipe 14.

The water temperature Which the regulator 38 will tend to maintain in the boiler and the 5 temperature at which the fan motor will be started or stopped, may be regulated by adjusting the position of the weight 42 along the lever arm 41. An incidental effect of this adjustment is to regulate the amount of time during which 10 the fan 47 will operate under given conditions. For example, if the weight 42 is set to maintain relatively high water temperature the fan will not operate as much of the time as it will in delivering an equal amount of heat when the 15 weight 42 is set to maintain relatively low water temperature.

The smoke-pipe 27 is made air-tight in order that the flue gases it conducts to the chimney 28 may surrender the maximum amount of heat 20 to the basement air and thus decrease fuel costs. Ordinarily, in the usual furnace installation a check door is located in the smoke-pipe near the boiler, but the air it admits at this location so cools the flue gases passing through the smoke- 25 pipe that most of the flue gas heat is wasted by escaping up the chimney. Also, deterioration of the smoke-pipe is ordinarily more rapid when air is admitted to it than is the case with the airtight design illustrated in the drawing. 30

For heating service water, an indirect water heater 49 is connected in a minor circulating system paralleling the main circulating system through the heat exchanger. This minor circulating system includes a pipe 50 leading from the 35 pipe 14 at the top of the boiler to the heater 49, and a pipe 51 leading from the heater to the return pipe 19 near the bottom of the boiler. The service water circulates from the bottom of a hot water storage tank. 52, through a pipe 53 upward 40 into and through a heating coil in the heater 49 and thence through a pipe 54 into the top of the storage tank. Water is supplied to the bottom of the hot water storage tank 52 through a pipe 55 that is connected to the supply pipe 22, and hot 45 water is delivered from the top of the tank through a pipe 86 that leads to the various positions throughout the building at which the hot water is utilized.

Circulation of water from the boiler through 50 the-heater 49 occurs because of the fact that the temperature of the water is lowered in imparting heat to the service water in the heating coil. Consequently, the column of water in the vertical return pipe 51 is cooler and denser than a corre- 55 spending column of water in the boiler, and the cool water column descends through the pipe 51 by gravity, causing circulation by natural convection.

The circulating water in the pipe 51 is utilized 60 to provide heat for evaporating the water in the humidifying tank 9. As shown, the humidifier is provided with a submerged heating coil 56 into which water may flow from the pipe 51 through a pipe 57 and from which it flows through a pipe 58 65 to the return pipe 19. The flow of water through the heating coil 56 may be regulated by a valve 59 in the pipe 57 and a valve 60 arranged to close the portion of the pipe 5f between the pipe 57 and the pipe 19. By manipulating these valves, the tem- 70 perature of the water in the humidifier may be controlled, thus regulating the rate of evaporation of the water and the humidification of the air circulating through the conditioning chamber. As a further means of controlling the action of the ⁷⁵ erably of the mercury type, mounted on the lever arm 41 closes and completes an electric circuit that leads from a power line 44 through conductors 45 to a motor 46 connected to a fan 47 dis5 posed in the lower part of the intake compartment 6. The fan is so directed as to increase the circulation of air through the system by forcing air from the intake compartment 6 into the discharge compartment 7 and upward through the 10 heat exchanger 10. The increased circulation of air through the heat exchanger results in conveying additional heat from the hot water circulating through it and consequently tends to reduce the temperature of the water in the boiler.

The additional heat transferred from the boiler water is conveyed by the air to the rooms being heated and raises the room temperature in response to the functioning of the thermostat 32.

When the predetermined normal temperature 20 in the rooms is restored, the thermostat 32 actuates the thermostat motor 33 to cause it to close the draft door 36 and to open the check door 37, thereby decreasing the rate of combustion of fuel in the firebox and reducing the amount of heat 25 supplied to the boiler.

When the temperature of the water in the boiler becomes reduced below a predetermined value, as a result of the action of the fan and of the reduced rate of combustion of fuel ef30 fected by the thermostat, the thermal expansion element 39 contracts and permits the weight 42 to pivot the lever arm 41 in such manner as to open the switch 43 and stop the fan motor 46, thereby reducing the amount of heat supplied to 35 the rooms and preventing the room temperature from exceeding the predetermined maximum.

If the predetermined normal temperature in the rooms is not restored within a short time, the temperature of the boiler water will con40 tinue to increase while the fan 47 is operating in spite of the cooling effect of the fan, and the water temperature regulator 38 will function, through a connection with the draft and check doors, to reduce the rate of fuel combustion and 45 prevent overheating of the boiler water. This action of the water temperature regulator will occur regardless of the fact that the thermostat motor 33 may be tending, at the time, to increase the rate of fuel combustion.

r.n To enable this result to be accomplished, the continuous chain 34 of the draft regulating mechanism is connected to the draft door and to the check door by means of pulleys 48, one of which is mounted on each door, the pulleys being arranged to rotatably receive the chain. The run of the chain at the sides of the pulleys 48 .opposite from the run thereof that is connected to the thermostat motor 33, is attached to the end of the lever arm 41, as shown. When the GO temperature of the boiler water exceeds a predetermined maximum, the lever arm 41 of the temperature regulator 38 is moved to the position shown in the drawing and in so doing actuates the chain 34 to close the draft door 36 and 65 to open the check door 37 independently of the action of the thermostat motor 33. As the thermal expansion element 39 which operates the arm 4i expands or contracts in accordance with temperature changes of the water in the boiler, 70 its action causes the temperature regulator 38 to actuate the draft door and the check door in modulating manner to maintain the temperature of the boiler water substantially constant. This arrangement prevents overheating of the boiler 75 water and prevents the formation of excess

2,128,203 humidifier, the amount of water surf ace exposed to the air may be regulated by covering a portion of the tank 9.

The level of the water in the humidifying tank 9 5 is maintained substantially constant by a floatoperated valve 61 which automatically admits water from a pipe 62 that is connected to the supply pipe 22 to replenish water evaporated in humidifying the air. To prevent corrosion of the io humidifier or the formation of scale therein, chemicals of the nature ordinarily Utilized in steam boilers for such purposes may be added to the water.

In front of the fan 4T and over the humidifying 15 tank 9, there is arranged a series of directing vanes 63 that turn the circulating air uniformly upward into the heat exchanger i 0 with minimum loss of energy.

Auxiliary air may be introduced into the cir20 culating system through an auxiliary air intake pipe 64 extending from the intake compartment 6 out of doors for admitting fresh outside air and having a damper 65 for controlling the volume of air admitted. A second auxiliary air intake pipe 25 66 opening into the basement is connected to the compartment 6 and is likewise provided with a damper 67 for controlling the volume of air admitted from the basement into the system.

During warm weather the air conditioning sys³⁰ tem is utilized for cooling and drying the air in the building. To adjust the system for this mode of operation, a valve 68 in the pipe 14 and a valve 69 in the pipe 19 are closed to isolate the heat exchanger 10 from the boiler, leaving the minor 35 circulating system through the service water heater 49 connected to the boiler. Cold water from the supply pipe 22 is then admitted to the heat exchanger through a pipe 70 having a control valve 71 which leads into the pipe i4. From the 40 pipe (4 the water flows through the upper bank of tubes 15 of the heat exchanger to the header 16 and then back through the lower bank of tubes 17 into the header 18 and the return pipe 19 from which it escapes through a discharge valve 72 into 45 a discharge pipe 73. Ordinarily, the water discharged through the pipe 73 is put to'some useful purpose, as for supplying a fountain and pool or for watering the lawn or garden, such use being suggested by a faucet 74 which is provided at the 50 end of pipe 73 that extends out of doors for attaching a hose. Refrigerated water or other cooling fluid may be circulated through the heat exchanger instead of water from the usual city supply.

For circulating the air through the circulating system while the cold water is passing through the heat exchanger, the fan motor 46 is operated to drive the fan 47 continuously. To provide for selectively operating the fan motor 46, a manually ο» operated push-button switch 75 is arranged to connect the conductors 45 which lead to the motor directly to the power line 44. Another pushbutton switch 76 is arranged in the circuit of the mercury switch 43 on the lever arm 41 and may be 65 opened to render the mercury switch inoperative while the system is being used for cooling.

The fan 47 forces the air upward first through the spaces between the lower tubes 17 and then through the spaces between the upper tubes 15 of 70 the heat exchanger. In this manner the air first comes in contact with and is cooled by the tubes containing water that has been wanned somewhat, and then the partly cooled air passes over the tubes containing the cold water. This is in 75 accordance with the counterflow principle of heat transfer wherein the wannest air comes in contact with the warmest tubes and the coolest air passes over the coldest tubes, the arrangement which is generally recognized as the most efficient for the transfer of heat between fluids. 5

During the period in which the apparatus is being used to cool the air, the supply of water to the humidifier 9 is interrupted by closing a valve 77 in the pipe 62, and the water is drained from the tank by opening a valve 78 in a drain- ic Pipe 79. When the warm air from the rooms comes in contact with the cold tubes of the heat exchanger, the excess water vapor in the air condenses upon the surface of the tubes, thus reducing the humidity of the air. The moisture 15 which collects on the tubes drips into the humidifier tank 9 and is drained away through the open drain-pipe 79.

While the air circulating system is being utilized to cool the air in the building, the boiler 2 20 may be used for heating the service water. To provide automatic regulation of the service water temperature, the thermostat 32 is rendered inoperative by adjusting it to a high temperature setting, in which position it wifi tend to hold the 25 draft door 36 open continuously and to hold the chimney check door 37 closed continuously. The adjustable weight 42 on the water temperature regulator 38 is then so positioned that the regulator 38 will operate to close the draft door 36 30 and open the check door 37 in opposition to the tendency of the thermostat when the desired service water temperature is attained. The regulator thus adjusted will maintain a low fire in the firebbx to heat the service water to a pre- 35 determined temperature without further attention to the apparaus other than refilling the fuel hopper 24, which ordinarily is necessary only at weekly intervals. Should changing weather conditions, such as occur in the spring or in the 40 fall, make it desirable to change the mode of operation of the apparatus from cooling to heating because of a sudden drop in temperature, it is merely necessary to shut off the flow of cold water through the heat exchanger and re- 45 connect it to the boiler by opening the valves 68 and 69. The hot water always available in the boiler provides instant heating effect and the continuously burning fire can at once be placed under the control of the thermostat 32 to bring 50 the air in the rooms to the desired temperature.

Although a specific air conditioning system has been described in detail herein for the purpose of clearly disclosing a practical embodiment of the invention, it is to be understood that the particu- 55 lar structure set forth is susceptible of modification without departing from the spirit and scope of the invention as defined by the subjoined claims.