US2903187A - Heating system - Google Patents

Description

p 1 9 L. H COYKENDALL 2,903,187

' HEATING SYSTEM Filed April 15, 1 955 /HEATING LOAD INVENTOR LegzflCbykendalZ ATTORNEY United States Patent O HEATING SYSTEM Leon H. Coykendall, Plainfield, N.J., assignor to The Babcock & Wilcox Company, New York, N.Y., a corporation of New Jersey Application April 15, 1955, Serial No. 501,600

3 Claims. (Cl. 237-8 This invention relates in general to an improved high temperature liquid heating system and more specifically, the invention relates, to apparatus for heating the water in a hot water heating system by using saturated steam.

In recent years high temperature and pressure water has been replacing steam as a means for space and process heating. A hot water heating system has such characteristics. that it maintains the heating surfaces at a substantially uniform temperature, minimizes piping complicity by eliminating steam traps and reduces heating losses because there is no condensate or steam lost to the atmosphere. The system preferably operates at pressures in the range of 60-240 p.s.i.g. and with water temperatures within the range of 300-400 F. Such temperatures make possible the use of the water as a source of heat for many applications besides space heating, such as providing heat for making low pressure steam in steam consuming processes, baking ovens and chemical processes where a uniform and high capacity supply of heat is required.

In the past hot water systems, the cool liquid from the circulating system has been caused to pass through a combustion fired heat exchanger wherein the water rises in temperature and is delivered at some controlled temperature. Because, in such prior art systems, the temperature is well above the boiling point of water at atmospheric pressure, there is maintained a pressure on the system sufiiciently high so as to preclude the Water from boiling as it is being heated. Therefore, in such hot water systems, the water temperature is always at a value below its boiling or saturated temperature, thus causing the water system to be designed for a pressure which is higher than the saturated boiling pressure of the water at the delivered temperature.

The combustion fired hot water heater for such systems is exposed to a rather large temperature gradient over the length of the hot water flow path in the heater. This creates a multiplicity of temperature expansion problems in the tubes or pipes which must be accounted for by the design of the heater. This multiplicity of differential temperature expansions requires that each section of the unit have a different provision for a temperature expansion and as such increases the complicity of the design, thus making the unit expensive.

Because there is no boiling taking place in the hot water heater, it is conventional to use a forced circulation type which requires that the safe operation of the heater be dependent upon the operation of a circulation pump. If for any reason the circulating pump fails, the high temperature products of combustion cause the stagnant water to boil and probably would result in the rupture of a tube, or other damage to the heater.

The present invention relates to a high temperature liquid heating system wherein vapor is supplied to a direct heat transfer exchanger and circulated heating liquid passes in direct heat transfer with the vapor causing condensing of the vapor heating the liquid.

In the practice of the invention, the vapor is generated r" ice in a standard vapor generating unit and supplied to the vapor space of a drum separate from the vapor generating unit and having a liquid level therein. The drum is sufiiciently large so that it has a large enough capacity for the size of the entire projected heating plant even though there may not be installed sufficient vapor generators to supply such a load. In the pertinent high temperature liquid heating system, the circulated liquid is heated by saturated temperature vapor so that the liquid is circulated at substantially saturated temperature upon leaving the direct heat exchange drum. Thus the operating and design pressure of the heaing system is maintained at an absolute minimum for the specified liquid temperature. Further, the vapor generator or generators can be of a standard type operated in a conventional manner, thus they would be the least expensive form of heat supply for the liquid heating system.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawing and descriptive matter in which I have illustrated and described an embodiment of my invention.

In the drawing, conventional fuel fired natural circulation vapor generators 2 and 3 furnish saturated vapor from the vapor space above the water level 4 and 5 in the drums 6 and 7 by the lines 8 and 9 to a direct heat exchanger including the drum 10. Connected to an outlet nozzle 12 and inlet nozzle 14 of the drum 10 is a hot liquid circulating system having a heat exchanger 16 arranged to heat any receiver or heating load such as a space and/or process.

The high temperature liquid flows through the system under the impulse of a circulating pump 18. The cooled liquid upon entering the drum 10 through the line 11 and the nozzle 14 is discharged into a long manifold 18 and thence into spray nozzle lines 20 which are distributed along the manifold and are arranged so that the liquid sprays into the vapor space above the liquid level 22 in the drum. The cool liquid coming in direct contact with the saturated vapor will condense the vapor and heat up the liquid and the pump 18 will then take suction on liquid which is substantially at a saturated temperature. The water level 22 in the drum 10 is maintained by a water level control 24 which in turn operates makeup valve 26 and blow-down valve 28 so as to either add or take liquid from the heating system to maintain the proper level during various heating load changes.

All of the vapor generated by the vapor generators 2 and 3 is condensed in the system. Therefore, the makeup feed for the vapor generators is taken from the circulated hot liquid system in the line 30 and distributed to the two vapor generators in accordance with their steam demands. This action is preferably accomplished by conventional boiler controls.

The vapor generators are fired by the burners 32 to maintain a particular vapor pressure in either the drums of the vapor generator or the direct heat exchanger drum 10. If either of the vapor generators 2, 3 is to be secured, the isolating valves 34, 36 may be used.

The present invention provides a hot liquid heating system which does not require a special and therefore expensive combustion fired heater. The heating system may be designed for any particular projected load and all that would have to be done toincrease the capacity of the system would be to add vapor generators in response to the load demands.

The pertinent system eliminates the need for a separate surge tank by providing for surge volume in the direct heat exchanger drum. Further, the present system is 3. designed for the minimum pressure consistent with the hot fluid temperature because it utilizes saturated temperature heating liquid.

While in accordance with the provisions of the statutes, I have illustrated and described herein a specific form of the invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features.

I claim:

1. In combination, a vapor generating means, a separate hot liquid heating system comprising a long horizontally disposed liquid heating drum having a liquid level maintained with predetermined narrow limits and separating its uppertsaturated vapor space from its lower saturated liquid space, said drum sized to accommodate the normal changes ofliquid volume of said liquid heating system within said limits, a heat transfer unit separate from said heating drum and arranged to transmit heat to a heat receiver, a circulating liquid system arranged to circulate saturated temperature liquid through said heat ing drum and heat transfer unit, conduit means for supplying saturated vapor from said vapor generating means to said heating drum, heat transfer means within said heating drum arranged to spray the cooled circulated liquid in direct heat transfer relationship with the saturated vapor, means for feeding a portion of the saturated circulated liquid to said vapor generating means, and means responsive to the liquid level in said drum to blow down liquid from said system upon a high liquid level in the drum and to inject cool make-up liquid into said system downstream of said heat transfer unit upon a low liquid level in said drum.

2. In combination, a vapor generating means, a separate hot liquid heating system comprising a long horizontally disposed liquid heating drum having a liquid level maintained within predetermined narrow limits and separating its upper saturated vapor space from its lower saturated liquid space, said drum sized to accommodate the normal changes of liquid volume of said liquid heating system Within said limits, a heat transfer unit separate from said heating drum and arranged to transmit heat to a heat receiver, a circulating liquid system arranged to circulate saturated temperature liquid through said heating drum and heat transfer unit, conduit means for supplying saturated vapor from said vapor generating means to said heating drum, a cool liquid distributing header disposed longitudinally of said drum below said liquid level, a plurality of liquid conduits rising from said header vertically and extending into said vapor space at spaced positions longitudinally of said drum, a liquid spray nozzle on each of said conduits arranged to spray liquid above said liquid level and directly into said vapor space and heat said liquid substantially uniformly throughout the length of said drum, means supplying the cooled liquid from said heat transfer unit to said header, means for feeding a portion of the saturated circulated liquid to said vapor generating means, and means responsive to the liquid level in said drum to blow down liquid from said system upon a high liquid level in the drum and to inject make-up liquid into said means supplying cooled liquid into said header upon a low liquid level in said drum.

3. A high temperature hot water system comprising a plurality of steam generators connected in parallel for generating steam, a steam to water heat exchanger connected in series with said generators, conduit means supplying saturated steam from said generators to said heat exchanger, said heat exchanger including an elongated horizontally disposed drum having a liquid level separating an upper steam space from a lower saturated water space, a submerged cold water header disposed in said water space, a conduit connected to said header and projected upwardly therefrom to extend into said steam space, a spray nozzle connected to the upper end of said conduit to spray relatively cold Water into direct heat transfer relationship to said steam whereby the cold water is heated to saturated temperature, a remotely disposed heat transfer unit arranged to transmit heat to a heat receiver, water circulating means connecting said heat transfer unit to said heat exchanger in a close circuit circulating saturated water from said water space and through said heat transfer unit whereby the heat content of the saturated water is reduced and returned to the header as relatively cold water, and means for maintaining the water level within said steam water heat exchanger, said means comprising a water level controller responsive to the water level in the drum to blow down the Water from said drum upon a high water level and to inject relatively cool make-up Water into said system downstream of said heat transfer unit upon a low liquid level from said drum.

References Cited in the file of this patent UNETED STATES PATENTS 188,201 Snowden Mar. 6, 1877 790,976 Peck May 30, 1905 2,292,023 Dickey Aug. 4, 1942 2,393,079 Wall Jan. 15, 1946 FOREIGN PATENTS 363,336 Great Britain 1932 475,767 Great Britain Nov. 25, 1937

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