US2743609A - Calorimeters - Google Patents

Description

May 1, 1956 P. scHULLER CALORIMETERS Filed April 29. 1952 .PAW

L7 bwLaM/MLV United States Patent CALRllt/IETERS Pierre Schuller, Decazeville, France, assignor to Usines Chimiques s lt/letallurgiques de Decazeville (Societe Anonyme), Decaaeville, France, a company of France Application April 29, 1952, Serial No. 284,884

Claims priority, application France May 7, 1951.

4 Claims. (Cl. 73-19f)) This invention relates to calorimeter devices for measuring the heat content of gases, and more particularly to calorimeters which are used for determining the heating power of fuels, especially gaseous fuels, by transferring the heat content from combustion gases produced by burning said fuel to water and measuring the resulting temperature elevation of the water.

Devices of this type, perhaps the most widely known and used type of which is 'the Junkers calorimeter, generally comprise a cylindrical combustion chamber having a burner mounted therein, and communicating with a nest of heat exchange tubes, usually made of copper base metal, surrounded with water and adapted to be traversed with the combustion gases resulting from the burning of the tested fuel in the combustion chamber. The heat exchange between the water and the combustion gases is effected by indirect transfer through the walls of the heat exchanger tubes. Calorimeters of this kind are chiefly utilized in laboratory work and accordingly are operated only at intermittent periods for effecting a test. Under such conditions of use, they have proved generally satisfactory.

However, when it is attempted to use such calorimeters in continuous operation for the measurement of caloric flux, this expression being used herein to designate the amount of heat capable of being supplied per unit time by the combustion of a fuel flowing continuously through a line, it is found that calorimeters of the above type are quickly rendered unserviceable due to corrosion of the heat exchanger tubes and other parts of the apparatus.

lt is an object of this invention to provide a calorimeter adapted for continuous operation without substantial co1'- rosion of component parts by the deleterious substances contained in combustion gases.

Another object is to provide a calorimeter which can be substantially constructed from stainless steel in order to increase its resistance to corrosion without at the same time decreasing its heat transfer efficiency.

A further object is to provide a calorimeter of improved thermal efiiciency providing increased accuracy in calorimetric measurements.

A further object is to provide a calorimeter in which heat transfer from the combustion gases to the water is effected by direct Contact rather than through an intervening metallic wall.

Still another object is to provide a calorimeter especially adapted for use in measuring caloric fluxes, i. e. the amount of heat supplied, or capable of being supplied, per unit time, by a gaseous or liquid fuel flowing continuously through a line.

it may be advantageous in various heating installations to regulate a caloric flux by controlling the composition and/or rate of iiow of a fuel through a line, in response to the instantaneous variations of the heating power of the fuel. For this purpose, a small sample of the fuel would be continuously tapped from the main supply and burnt in a calorimeter so as continuously to determine the instantaneous heating power of the fuel, means responsive rice to the indications of the calorimeter being provided for introducing corrective modifications in the rate of supply of the fuel.

lt is, in this connection, an object of the invention to provide an improved calorimeter especially adapted for continuously ascertaining the instantaneous heating power of a liquid or gaseous fuel over prolonged. periods of time with the purpose of modifying the rate of supply of the fuel in accordance with any variations detected in the said instantaneous heating power.

The above and other objects of the invention are obtained by providing a calorimeter for measuring the heat content of a gas, comprising means defining a flow path for the gas, means defining a ow path for water, said flow paths having at least a common portion in which said gases and water are in direct contact, and means for determining the temperature elevation of said water along its said flow path.

The water is preferably caused to stream downwards in a thin uniform vein in counterliow relation to and in direct and intimate contact with an upwardly iiowing vein of the gas. In this way, heat transfer instead of being effected indirectly through metallic walls: as in the conventional type of calorimeters using heat exchanger tubes, is effected directly without an intervening metallic wall. The heat transfer is thus rendered more complete, the thermal efiiciency is increased, and furthermore, since conductivity of the metal is no longer relied upon for the heat exchange process, the parts of the apparatus in contact with the corrosive gases may be made of stainless steel or the like, instead of having to be made from such high-conductive metals as brass, etc., which are not adapted for resisting corrosion.

A further consequence of the streaming or direct contact principle of operation of the calorimeter of the invention is that the condensation water of the combustion gases, which contains the corrosive agents such as sulfuric acid responsible for corrosion of the metallic parts of the apparatus, is greatly diluted owing to the direct and intimate contact between the gases and the water circulated through the apparatus.

Fig. l is a view in vertical axial section of one exemplary embodiment of a calorimeter according to the invention, and

Fig. 2 is a transverse section on line II--II of Fig. l.

As shown in the drawings, a combustible gas or any other type of fuel of which the heating power is to be tested, is fed through a line 2 into a burner nozzle 1 together with air supplied through a line 3, so that the mixture of fuel and air will burn in the nozzle of burner 1. The burner assembly 1 is arranged within a cylindrical enclosure 4 defining an inner combustion chamber and having an ignition device such as a sparking plug S projecting into it. The combustion gases escaping out of the top of cylindrical enclosure i through an annular array of ports 6 formed therein enter into an annular space 7 defined between the outer wall of the enclosure 4' and a surrounding cylindrical liner member 8 suitably secured as by welding to a radially projecting flange 8a of the enclosure 4. The combustion gases then rise through annular space 9 between cylindrical liner 3 and outer housing 10 finally to discharge through a flue l1 into a suitable stack not shown. In the drawing, the solid arrows indicate the path of flow of the combustion gases.

Water is supplied through an inlet pipe 12 passing through the flue and projecting axially into the top of the housing l0. The water from the outlet of pipe 12 falls into a shallow tray i3 overlying inner cylindrical enclosure 4, the bottom of the tray being defined by the top of this enclosure and the opstanding sides of the tray being dened by an upward extension of cylindrical liner 8. The upstanding walls of the tray are formed with perforations la through which the water overflows so as to stream in a thin cylindrical sheet along the outer surface of cylinder 8 in the annular space 9, in which it tio-ws in direct and intimate contact with the Y combustion gases rising in the form of a thin upllowing cylindrical sheet through said annular space, in counterflow relation with the downilowing sheet of water, so that heat exchange occurs in ideal conditions. The conventional tubular nests used for heat exchange, with their attendant drawbacks such as clogging requiring cleaning at frequent intervals, are thereby eliminated. The perforations 14 should be small enough to provide for a build-up of water to a substantial level in the tray t3, thereby averting possible irregularity in the water supply, and enabling successfull operation even where the calorimeter assembly has not been perfectly levelled so that it stands at a slight angle to the vertical; moreover, the numerous perforations spaced all around the periphery of the tray provide for a uniform film of water streaming over the outer wall of cylindrical member l.

While for clarifying the illustration, the annular space 9 has been somewhat exaggerated in width in the drawings, actually the width of this interval should be selected as small as consistent with the permissible loss of pressure head over the gas-flow circuit of the combustion gases, so that both the gases and the water should be in the form of thin sheets or veins in the area of their common flow path. The same applies to the interval 7 in which the combustion gases flow in indirect heat transfer relationship with the water through the cylindrical wall 8. Desirably moreover, this wall 8 is formed with a plurality of small spaced perforations whereby the water may flow over both faces thereof in contact with the combustion gases.V Thus, the cylindrical wall 8 may desirably be provided in the form of a very tine mesh Wire netting or the like.

As the result of the ow both of the water and the gases in the form of very thin or shallow sheets or veins, as described, a complete transfer of the heat content from vthe latter to the former, as well as complete absorption of said heat by the water, is obtained.

The water streaming off the cylindrical wail la? runs through or crosses the ow path of the gases at the point where the gases pass from the annular space into annular space 9i, and this intersection of both flow paths further promotes the desired heat transfer. The water iirst collects in a lower tray .l so as to bathe the lower end of the inner enclosure wall 4 and then overflows therefrom into an outlet .i6 leading into a vertical tube i7 `provided with a suitable theremometer l for reading the temperature of the outilowing water, and finally escapes through an outlet pip-e il). The dotted arrows indicate the low circuit of the water in the apparatus.

A calorimeter according to the invention may be described as being of the stream type, or 'further as operating on the principle of direct contact between the water and the combustion gases. In addition to the previously listed advantages thereof, such a calorimeter further possesses superior thermal efficiency. In a calorimeter employing a tubular heat exchanger, the gases flowing through the tubes transfer the heat content thereof to the tube walls and thence the heat is transferred to the surrounding water by conductivity. ln such a calorimeter, all of the gas filaments are not in direct contact with the tube walls; thus, in the case of 6 mm. diameter tubes, the central gas filament is spaced 3 mm. from the tube wall. Similarly, all the water filaments are not in contact with the tubes, since some may be spaced from the outer tube walls by as much as several millimeters. In the improved calorimeter of this invention, on the other hand, the fact that there is no separating wall between the gases 4and the water increases the heat exchange coetlicicnt. As concerns the gas vein, which is less than 3 mm. in thickness or depth, the heat transfer conditions are no less favorable than those prevailing in a tubular calorimeter. On the other hand, as far as the water is concerned, the depth of the vein is less than 1 mm. in depth so that the conditions are much more favorable. Moreover, heat transfer does not merely occur by contact, but partly also by a mixture between the stream of gas and the stream of water flowing in counterflow relation, thereby considerably improving the conditions of heat transfer owing to the very high heat exchange coeiiicient in the case of condensing vapors. In actual practice, it has been found that the temperature difference between the etlluent water and the effluent gases, which difference characterizesthe eiciency of the heat transfer is as low as 2 C. in a calorimeter unit constructed in accordance with the invention, as against 4 C. in the case of a conventional calorimeter using tubular heat exchange means. The said dilference can be reduced even further in a calorimeter according to the invention by providing suitable heat isolation for the upper water tray i3, and it can even be substantially reduced to zero.

Moreover, the condensation water of the combustion gases is diluted in the water flow of the apparatus, thereby simultaneously diluting the corrosive substances contained therein, so that the corrosion of the various parts of the apparatus in contact with the combustion gases is greatly reduced.

As stated, the calorimeter of the invention can readily be constructed out of stainless steel, instead of the conventional copper-base alloys hitherto required.

As a final advantage, the pressure loss through the combustion gas flow circuit is much lower than in a conventional tubular heat exchange calorimeter.

It will be understood that many modifications may be made in the design and construction of the irriproved calorimeter of the invention within the scope of definition thereof as set forth in the ensuing claims.

What I claim is:

1. In a calorimeter for measuring the heat content of gases, meansV comprising an innermost, an inner and an outer spaced substantially vertical cylindrical walls detining a first annular space between said innermost and said inner, and a second annular space between said inner and said outer walls, means for discharging water down the outer surface of said inner wall, container means surrounding the lower end of said innermost wall and underlying the lower end of said inner wall for collecting and retaining a body of said water discharged down said outer Y surface to a free level spaced below the lower end of said inner wall so as to provide an annular communication orifice between said rst and said second annular space, means for discharging said gases downwardly through said first annular space, outwardly through said annular orifice and upwardly through said second annular space in intimate heat transfer relation with said downwardly streaming water, and water outlet means receiving the overflow from said container means, and means for determining the temperature of the outflowing water.

2. in a calorimeter for measuring the heat content of the combustion gases from a fuel, in combination, a first cylindrical wall defining a combustion chamber and means for burning said fuel therein, a second cylindrical wall surrounding and spaced from said rst wall and defining a rst annular space, a' third cylindrical wall surrounding and spaced from said second wall and defining a second annular space, means sealing the tops of said chamber and said first space and defining water-retaining means thereon, a water inlet discharging into said water-retaining means, overflow means for streaming the water from said retaining means over and down the outer surface of said second cylindrical wall, a further water-retaining means surrounding the bottom of said combustion chamber and underlying the bottom end of said second cylindrical wall to receive and retain said streaming water up to a free level spaced below said bottom end of said second wall to provide an annular communicating orifice from said first to said second annular chamber; communicating apertures in the top of said first cylindrical wall for passing the combustion gases from said burnt fuel down said first annular space, through said communicating orifice and into and up said second annular space and out therefrom into a flue, water outlet means receiving the overiow from said further retaining means, and thermometer means for measuring the rise in water temperature from said water inlet to said Water outlet.

3, Calorimeter as claimed in claim 2, wherein said second cylindrical wall is perforated.

4. ln a calorimeter for measuring the heat content of a fuel, a combustion chamber provided with means for burning a fuel therein, a pair of inner and outer substantially vertically disposed cylindrical walls arranged concentrically around the combustion chamber, said walls heilig spaced radially apart from each other to define between each other an annular gap, means for conveying combustion gases from the combustion chamber and introducing them into the lower end of the gap so that such gases flow upwardly in the gap between the walls, means for exhausting such gases from the upper end of the gap, means for introducing liquid into the upper end of the gap and causing it to ow in a sheet over the outer surface of the inner wall so that the liquid. streams down the outer surface of the inner wall in direct contact rela tion with the upwardly flowing gases, means for collecting the liquid at the lower end of the gap and means for determining the temperature elevation of said liquid in the collecting means.

References Cited in the le of this: patent UNITED STATES PATENTS 1,381,714 Laird June 14, 1921 FOREIGN PATENTS '171,246 Great Britain Nov. 17, 1921

Claims (1)

1. 4. IN A CALORIMETER FOR MEASURING THE HEAT CONTENT OF A FUEL, A COMBUSTION CHAMBER PROVIDED WITH MEANS FOR BURNING A FUEL THEREIN, A PAIR OF INNER AND OUTER SUBSTANTIALLY VERTICALLY DISPOSED CYLINDRICAL WALLS ARRANGED CONCENTRICALLY AROUND THE COMBUSTION CHAMBER, SAID WALLS BEING SPACED RADIALLY APART FROM EACH OTHER TO DEFINE BETWEEN EACH OTHER AN ANNULAR GAP, MEANS FOR CONVEYING COMBUSTION GASES FROM THE COMBUSTION CHAMBER AND INTRODUCING THEM INTO THE LOWER END OF THE GAP SO THAT SUCH GASES FLOW UPWARDLY IN THE GAP BETWEEN THE WALLS, MEANS

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