US3238998A

US3238998A - Heat exchange devices

Info

Publication number: US3238998A
Application number: US132338A
Authority: US
Inventors: Moore Robert Edwin; Keyes Jack
Original assignee: Deutsche ITT Industries GmbH
Current assignee: TDK Micronas GmbH; International Telephone and Telegraph Corp
Priority date: 1961-08-18
Filing date: 1961-08-18
Publication date: 1966-03-08
Anticipated expiration: 1983-03-08

Description

March 8, 1966 R. E. MOORE ETAL 3,238,998

HEAT EXCHANGE DEVICES 3 Sheets-Sheet 1 Filed Aug. 18, 1961 z y 5/ MW v im Q M? g March 8, 1966 R. E. MOORE ETAL HEAT EXCHANGE DEVICES 3 Sheets-Sheet 2 Filed Aug. 18, 1961 March 8, 1966 R. E. MOORE ETAL 3,233,993

HEAT EXCHANGE DEVICES Filed Aug. 18, 1961 5 Sheets-Sheet 5 wil .PM/ezvers 5 fa? E'Maore {Q ac yes.

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To lP/I D/A 770 Law 75 United States Patent 3,238,998 HEAT EXCHANGE DEVICES Robert Edwin Moore, Winnetka, and Jack Keyes, hark Ridge, liL, assignors, by mesne assignments, to internationai Telephone and Telegraph (Iorporation, New

York, N.Y., a corporation of Maryland Filed Aug. 18, 1961, Ser. No. 132,338 1 Claim. (Cl. 16540) This invention relates to heat exchangers and more particularly is concerned with an apparatus providing improved circulation of liquid for effecting more elficient heat transfer.

In one specific aspect, the invention is concerned with providing an improved indirect water heater of the pumped or mechanical circulation type characterized by the feature that its heat exchange surfaces and temperature responsive circulation control element are exposed to liquid in continuous circulation within a heat exchange chamber to respond uniformly to temperature conditions of the liquid in the chamber.

This arrangement has the important advantages of preventing overheating of the water being heated to avoid liming of the heat exchange surface and of providing precise control over the temperature of the domestic water circuit served by the heater.

In a presently preferred form, these advantages are best obtained by mounting a pump impeller directly in the heat exchange chamber to create more turbulence and better circulation and thereby raise the overall capacity of the heat exchanger. This arrangement eliminates need for a separate pump casing. Moreover, for units of the same size, greater capacity is realized.

A related application to a hot water boiler is contemplated wherein a pump impeller is mounted directly in the water space of the boiler to create additional turbulence and circulation internally in the water space of the boiler for raising the efliciency of heat transfer through the heat exchange surfaces that divide the combustion chamber and Water space. In this arrangement the impeller may be sized to provide sufiicient power to circulate the water through the hot water system.

The principal object of the invention is to provide heat exchange methods and apparatus creating improved circulation of liquid for effecting more eiiicient heat transfer.

Another object of the invention is to provide a heat exchange device having an impeller mounted directly in the liquid space of a heat exchange chamber to create added turbulence and circulation of the liquid over the heat exchange surfaces.

Another object of the invention is to provide an indirect water heater having its heat exchange surfaces and circulation control element located for exposure to water in a common water space in which the heated water is made to circulate continuously.

A related object is to provide an indirect water heater of the above type and wherein an impeller is mounted directly in the water space to provide improved circulation therein.

Still another object of the invention is to provide a hot water boiler having its water space equipped with an impeller for providing increased internal circulation and more eflicient heat transfer.

Other objects and advantages of the invention will become apparent during the course of the following decription.

In the accompanying drawings froming a part of this specification and in which like numerals are employed to designate like parts throughout the same:

FIG. 1 is a generalized perspective view of an instantaneous type indirect water heater unit constructed in accordance with this invention;

3,238,998 Patented Mar. 8, 1966 "ice FIG. 2 is a sectional view throughout the heat exchange chamber of the unit of FIG. 1, and also illustrating the side mounted drive motor for the internally mounted impeller employed in accordance with the teachings of this invention;

FIG. 3 is an enlarged fragmentary sectional view, better illustrating the details of construction of the impeller;

FIG. 4 is a simplified wiring diagram of the motor control circuit;

FIG. 5 is a side elevational view of an alternative form of indirect water heater unit;

FIG. 6 is a longitudinal sectional view through a bypass valve utilized in the unit of FIG. 5; and

FIG. 7 is a vertical sectional view illustrating an improved hot water boiler equipped with an internally mounted circulating pump impeller.

Referring now to the drawings, a complete indirect water heater is shown in FIG. 1 for purposes of illustrative disclosure as comprising a hot Water storage tank 20, a separate shell or casing 21 located above the tank and defining a heat exchange chamber 21C (FIG. 2) having a liquid outlet connection fitting 22 to a length of return piping 23, that is, carried through a liquid inlet of the storage tank and preferably terminates adjacent the lower end of the storage tank. A supply pipe 24 is connected between a liquid outlet of the storage tank 20 and a liquid inlet 25 to the heat exchange chamber. The supply piping 24 is extended a short distance below the top of the storage tank 20 to function as a dip tube and permit air to be trapped at the top of the storage tank to act as an air cushion for equalizing pressures resulting from temperature induced volume changes of the heating water.

The storage tank 20 may be fired with gas, oil or electricity, and suitable facilities for this purpose are located within its base section 20B. The storage tank should also be equipped with control facilities of any well known type for maintaining the liquid contained therein at a predetermined fixed temperature.

In FIG. 1 a separate Water circuit 26 is shown entering the casing 21 at 27 and is shown leaving the casing :at 28. As is best shown in FIG. 2, this separate circuit is equipped with a heat exchange element 29 submerged in the liquid contained in the heat exchange chamber. The element 29 is represented as a coil of tubing of sufficient length to transfer the required quantity of heat. For convenience of reference, this separate circuit is hereinafter referred to as the faucet water circuit, while the Water which is recirculated between the heated storage tank 20 and the heat exchange chamber 21C is referred to as the heating medium water. In the arrangement described, the faucet water never mixes with the heating medium water.

Among the advantages of the arrangement shown in FIGS. 1 and 2 is the fact that the temperature at the heat exchange surfaces for the faucet water circuit is markedly lower than in the case of a direct fired heater. This hecomes particularly important in hard water areas since it minimizes the amount of lime precipitated on the heat exchange surfaces and, therefore, the initial capacity and efliciency of the present heater unit is maintained substantially unimpaired throughout long periods of service.

Since the only heated surfaces exposed to relatively corrosive water are those of the coiled heat exchange element 29, only this coil need be of more expensive non-corrosive material. All other parts, such as the storage tank '20 and the casing 21 for the heat exchange chamber, contact only the heating medium water. Since the heating medium water flows in a closed system, the small amount of oxygen and air originally present reacts chemically with the steel and iron parts during initial operation and thereafter the heating medium water is relatively non-corrosive.

In accordance with this invention, the temperature to which the faucet water is heated is regulated by an automatic temperature sensitive flow control valve 30 of any suitable type located in the flanged connector body 22 that connects the piping 23 for returning heating medium water from the heat exchange chamber in casing 21 to the storage tank 20. This flow control valve 30 has a temperature sensitive element 301" projecting into and directly exposed to the heating medium water in the heat exchange chamber 21C to regulate circulation of the heating medium water between the heat exchange chamber and the heated storage tank 20. In general, the valve closes to terminate such circulation when the temperature of the heating medium water in the heat exchange chamber reaches a preset maximum value which preferably is somewhat less than the temperature maintained in the storage tank and the valve opens to allow circulation when the temperature of the heating medium water in the heat exchange cham ber falls below some pre-selected minimum value.

Preferably, the range of the temperature sensitive control element is restricted within narrow limits to maintain the faucet water at approximately a constant temperature. An important advantage of the arrangement is that the automatic valve operates in the heating medium water which is less corrosive than the faucet water, and it therefore encounters fewer servicing problems. It is also advantageous that the automatic valve may be adjusted to maintain, in the heat exchange chamber 21C, a somewhat lower temperature than is maintained in the storage tank 20, this minimizes precipitation of lime and yet the capacity of the unit is unchanged since the temperature of the heating medium water in the storage tank is not changed.

In the arrangement of FIGS. 1 and 2 it will be noted that the heat exchange surfaces of the coil 29 for the faucet water circuit and the temperature sensing element of the automatic flow control valve 30 are both exposed to the heating medium water in the heat exchange chamber. This arrangement to be effective in preventing overheating of the faucet water for avoiding liming of the heat exchange surfaces and to be effective for providing precise control over the domestic water temperature, requires proper circulation of the heating medium water within the heat exchange chamber 21C. In the absence of active internal circulation, stratification and loss of control of temperature can result. This problem has been answered by mounting a pumping element 32 directly in the heat exchange chamber 21C with the pumping element being controlled to operate for circulating the heating medium water across the heat exchange surfaces and the flow control element at all times when the system is in use.

The internally mounted pumping element 32 is illus trated as a single suction, radial discharge type impeller and it is shown mounted on the drive shaft of an externally mounted motor 33 anchored on the side wall of the casing 21 and having its drive shaft projecting through this side Wall and into the heat exchange chamber to receive the impeller. The axis of the impeller 32 is aligned with the supply piping 25 for the heating medium water from the storage tank 20 and this piping is extended through the heat exchange chamber to provide a suction inlet passage leading directly to the impeller.

As best shown in FIG. 3, a conventional seal ring assembly 34 is shown sealing the entrance for the motor drive shaft at the suction side of the impeller, a loosely mounted seal ring 35 is provided to seal between the rotatable inlet stub 323 of the impeller and the flared end 25F of the suction inlet pipe 25. The seal ring 35 may be of Teflon or of other suitable lubric seal face material and it has relatively flat broad surfaced side faces to mate with and seal against the end face 25F of the suction inlet tubing. In addition, this seal ring has a feather edge 35F on its inner periphery to provide a seal against the impeller inlet stub. With this arrangement the pressure differentials acting upon the seal ring maintain it in stationary engagement against the inlet piping while the feather edge accommodates rotation of the impeller stub with but a minimum of wear.

The internally mounted pump impeller arrangement offers a number of important advantages. The discharge from the periphery of the impeller 32 is distributed in substantially all directions within the casing, and this provides additional turbulence and results in increased efiicicncies of heat exchange, thereby raising the over-all capacity of the heat exchanger beyond that which would normally be expected. Moreover, internal mounting of the pump impeller eliminates need for separate pump casing and thus reduces the cost of the unit.

When no water demand is made on the heater it is preferable to stop the pumping element and for this purpose a temperature sensitive switch 36 is positioned in the cold water inlet line 27 of the faucet water circuit at a point adjacent the casing 21 so that it may respond upon expansion of faucet water caused by heating of the stagnant water in the coiled heat exchange element. In FIG. 4 the switch 36 is shown connected in series in the power supply circuit for the motor 33. When there is no demand upon the faucet water circuit the faucet water standing in the coil 29 gradually heats up and expands and thereby transmits heat back to the inlet connection to open the switch 36 for stopping the drive motor 33 of the pumping element. Upon a draw of water from the faucet water circuit fresh cold water passing the temperature sensitive switch actuates it to reclose the circuit to the pumps drive motor.

For initially filling the unit with water a bleeder hole 27H (FIG. 2) may be provided in the inlet connection for the faucet water circuit at a location internally of the casing 21, and water will flow from the bleeder hole to fill the heat exchange chamber and from there will flow into the storage tank. During this filling operation air is trapped to form a cushion within the top of the storage tank 2t). In lieu of the illustrated bleeder hole arrange ment a conventional pressure reducing valve and relief valve can be utilized in the same fashion as on a hot water heating system boiler.

In normal operation the water in the storage tank 20 is maintained at a predetermined temperature and circulation between the storage tank and the heat exchange chamber is controlled by the temperature sensing element 30T of the flow valve 30 for maintaining the heating medium Water that is in the heat exchange chamber 21C within some predetermined range of temperature. When no demand is placed upon the faucet water circuit, this is sensed by the temperature responsive switch 36 in the inlet faucet water line and the power supply circuit to the motor 33 is held open. When faucet water is drawn, however, the cold water entering past this switch 36 closes it and energizes the motor for driving the pump impeller 32 to maintain a condition of turbulence and eflicient circulation throughout the heat exchange chamber. This creates efiicient heat transfer from the heating medium water to the faucet water circuit and also subjects the temperature sensing element 301 of the automatic flow valve to the true temperature conditions within the heat exchange chamber. This flow valve opens and closes as necessary for maintaining the heating medium water in the heat exchange chamber within the selected temperature range.

An alternative form of indirect water heater unit is illustrated in FIG. 5 wherein a motor-pump unit 40 is mounted externally of the casing 21. In this arrangement any suitable array of internal bafiie and nozzles (not shown) are provided Within the heat exchange chamber 21C to permit the external pump to create the desired flow distribution and internal circulation necessary for efiicient heat transfer from the heating medium water to the faucet water circuit. The principal components such as the storage tank 20, the casing 21 of the heat exchange chamber, the supply and return

lines

24 and 23, respectively, for the heating medium water, and the pump motor control switch 36 may be essentially the same in the FIG. arrangement as in the FIG. 1 arrangement. The external motor pump unit is shown connected in line in the piping 23 to return heating medium water from the heat exchange chamber of casing 21 to the storage tank 20. In addition, the return piping 23 is shown equipped with a T-fitting 41 on the discharge side of the motorpump unit and a by-pass line 42 extends from this T- fitting and into a temperature responsive bypass valve 43 that is connected into the supply piping 24- for automatically controlling flow from the storage tank to the heat exchange chamber.

One form for this temperature responsive automatic flow controlling valve is illustrated in FIG. 6. The valve includes an elongated hollow casing 44 having an inlet 441 at one end and connected to the supply pipe 24 for reeeiving hot water from the storage tank 20, having a side inlet 44R for receiving water recirculating from the bypass line 42 and having a set of discharge outlet holes 44D at its opposite end and located to discharge into the heat exchange chamber.

The outlet end of this valve is externally threaded as indicated at 44T to engage and seal in the side wall of the casing 21. An internal valve chamber 45 is provided adjacent the inlet end and is equipped with a plate or diaphragm 46 having a central offset 468 providing a spring seat that is encircled by a set of holes 46H arranged in an annular ring about this offset to provide through this chamber 45, a flow passage for heating medium water from the storage tank 20. An internal annular seal face 44F is provided intermediately along the casing and faces a seal face 46F provided by the diaphragm plate.

A seal sleeve 47 of a length somewhat less than the distance between these opposing seal faces is disposed in sealingly slidable relation within the casing and is shown engaged in sealing relation against the internal seal face 44F provided by the casing. In this position it blocks recirculating flow from the by-pass line 42 through the side inlet 44R. A rigid hat-shaped plate or piston 48 is located within the end of the seal sleeve 47 and has an actuating rod 49 connected to a temperature sensing element 50 which is arranged to respond and drive the rod 49 and piston 50 towards the diaphragm 46 when the temperature of the heating medium water Within the heat exchange chamber rises to some pre-selected value. A return spring 51 reacts between the diaphragm 46 and piston 48 to resist this movement and over travel spring 52 within the movable sleeve 47 and reacting between an end flange 47F thereof and the piston 48 transmits cushioned forces to the sleeve 47 to drive the sleeve against the seal face 46F of the diaphragm for shutting off the circulation of water from the storage tank and for establishing a flow circuit for the by-pass line 42.

Thus, when the temperature of the heating medium water in the heat exchange chamber exceeds a certain value the temperature sensing element 50 at the inner end of the by-pass valve casing 44 expands to drive the rod 49 outwardly and open the by-pass line 42 and seal the main supply line 24. Continued operation of the pump at this time provides continued recirculation through the by-pass line and through the heat exchange chamber and maintains high efiiciency of heat transfer.

When the temperature of the heating medium water in the heat exchange chamber falls below a certain value, the return spring 51 in the by-pass valve becomes effective to return the piston 48 and hence the sleeve 47 to open the main supply line and close the by-pass line; and upon continued operation of the pump, hot water is circulated into the heat exchange chamber to raise the temperature of the heating medium water therein.

While the temperature sensitive switch element 36 is again shown on the cold water inlet line 27 of the faucet water circuit for controlling the motor operation, a switch 6 responsive to pressure differentials in the faucet water circuit may also be employed for this purpose. In such an arrangement, each time faucet water is drawn off, a pressure drop, occurring in the faucet water circuit is sensed for turning on the motor-pump unit 40.

A hot water boiler incorporating certain principles of this invention is illustrated in FIG. 7 and includes a shell or casing 60 having internal walls 61, 62 and 63 and an external side wall 64, defining a combustion chamber 65. -A side mounted burner unit 66 of the oil or gas fired type is shown mounted for association with the combustion chamber 65. The shell has additional internal walls 67, 68, 69 and 70 providing exhaust flow passages for conducting combustion gases to a stack 71.

The boiler has an enclosed water space 72 bordered by an external wall 73 and internal walls 63, 67, 68, 69 and 70. A hot water supply riser pipe 74 is shown exiting from the top of the boiler for connection to radiation gear of a hot water heating system. A liquid return line 75 from the radiation gear of the hot water heating system is shown entering the bottom of the boiler and is extended through the liquid space 72 to provide a suction intake passage communicating directly with the suction eye of an impeller 32 that is mounted directly in the liquid space. The impeller 32 is of the single suction, radial discharge type and is driven by an externally mounted motor 3-3 having its drive shaft projecting through the Wall 73 for securement to the impeller. A conventional seal ring assembly 34 is shown sealing the access opening for the drive shaft and a Teflon ring 35 encircles the suction stub 328 of the impeller and has a feather edge 35F on its inner periphery in sealing contact therewith. Thus, the pump seal and mounting arrangement may be essentially identical with that illustrated in FIG. 2 in the case of the indirect water heater.

It should be understood that in many hot water heating system installations the internally mounted impeller 32 may constitute the sole means for circulating hot water through the radiation gear of the system. The internally mounted impeller arrangement is also useful in installations wherein a separate circulation pump is provided for securing additional capacity. With either arrangement, however, the internally mounted impeller produces a radial discharge about its periphery to set up marked internal turbulence and recirculation within the liquid space, and this creates a continuous flow of liquid across the heat exchange surfaces provided by internal walls 63, 67, 68, 69 and 7t Significantly improved heat transfer efficiencies are accomplished in this fashion.

It will now be apparent that the objects of this invention have been accomplished in that improved heat exchange techniques are disclosed for creating improved liquid circulation and turbulence to achieve more efficient heat trans-fer. While the invention is disclosed in connection with liquid heating equipment, in its broader aspects, it is also applicable to liquid chilling devices.

It should be understood that the description of the preferred form of the invention is for the purpose of complying with Section 112, Title 35, of the US. Code and that the claim should be construed as broadly as prior art will permit.

What is claimed is:

An indirect water heater comprising a heated storage tank having a liquid inlet and a liquid outlet and arranged to maintain liquid stored therein at a predetermined temperature, means providing a heat exchange chamber having a liquid inlet communicating with the first named liquid outlet and having a liquid outlet communicating with the first named liquid inlet, a separate liquid flow circuit having a portion thereof disposed in said heat exchange chamber in heat exchanging relation with liquid therein, means for circulating liquid between said heated storage tank and said heat exchange chamber to maintain liquid in said chamber within a predetermined temperature range and including an impeller disposed in said heat exchange chamber in direct contact with liquid therein and having a suction intake passage communicating directly with the liquid inlet thereof, motor means for rotating said impeller to stir liquid within said chamber and to draw liquid from said storage tank through said liquid inlet of said chamber and said suction intake passage, and to discharge liquid from said impeller into said chamber in various directions to create internal turbulence and circulation across said heat exchange surfaces to improve heat transfer across said surfaces while concurrently returning liquid from said chamber to said storage tank, an automatic valve for regulating circulation of liquid between said heated tank and said heat exchange chamber without interrupting internal circulation in said chamber, said valve being responsive to the temperature of liquid in said heat exchange chamber, and means for deactivating said motor means only during the absence of a draw of liquid through said separate circuit.

References Cited by the Examiner UNITED STATES PATENTS 8 2,038,982 4/ 1936 Broderick 2378 2,073,276 3/1937 Ensign 16540 2,190,382 2/1940 Moore 126-36'2 2,254,387 9/1941 Olcott 2573 13 2,347,989 5/1944 Burnham l109 2,483,275 9/1949 Gregor 2573 14 2,626,107 1/1953 Rollins 23763 2,762,652 9/1956 Carter 257314 2,800,307 7/1957 Putney 25773 2,875,027 2/1959 Dye 109 2,979,308 4/1961 Putney 25773 FOREIGN PATENTS 257,593 8/1925 Great Britain.

JAMES W. WESTHAVER, Primary Examiner. FREDERICK L. MATTESON, JR., Examiner.

CHARLES SULKALO, V. M. PERUZZI,

Assistant Examiners.