US2689478A

US2689478A - Calorimeter

Info

Publication number: US2689478A
Application number: US150962A
Authority: US
Inventors: Clayton H Barnard; James E Mcevoy
Original assignee: Bailey Meter Co
Current assignee: Elsag Bailey Inc
Priority date: 1950-03-21
Filing date: 1950-03-21
Publication date: 1954-09-21
Anticipated expiration: 1971-09-21

Description

Sept. 21, 1954 c. H. BARNARD ETAL CALORIMETER Filed March 21, 1950 INVENTURS AND CLAYTON H. BARNARD JAMES E. MQEVOY BY A RNEY mwEo E4 Patented Sept. 21, 1954 2,689,478 CALORIMETER Clayton H. Barnard, South Euclid, and James E.

McEvoy, East Cleveland, Ohio. assignors to Bailey Met-er Company, a corporation of Dela- Ware Application March 21, 1950, Serial No. 150,962

4 Claims. 1

Our invention is in connection with calorimany, and specifically offers an apparatus for compensating gas calorimeters which determine the lower heating value of gaseous combustibles so that the higher heating value of the combustibles may be obtained.

In the United States commercial, gaseous fuel is usually sold to customers on the basis of its higher heating value. Objection is raised when comparison is made to countries or cities which base their rate on the lower heating value. It might be possible to meet the objection if the high and low heat values maintained a constant ratio as the constituents of the fuels varied. It would then appear that a customer in the United States obtained a consistently proportional amount of heat for his money compared with the continental user, and the problem of obtaining equality would evolve into a simple matter of economics.

However, the ratio of higher to lower heat values varies with the hydrogen content of the fuels. Therefore, the United States customer finds that the high heat value of his fuel mounts with hydrogen content increase while his cost rises as some definite function of such increase. However, the heat actually available, namely the lower heat value, does not rise by the same function.

By theterm heat available reference is to that quantity of heat of the combustion proc ess which the customer ordinarily transfers to a working fluid by a heat exchanger. Commercial heat exchangers do not utilize the heat residual within the steam of combustion as heat oivapor ization, exhaustion of the products of combustion taking place prior to condensation.

As traditional usage continues to influence the system of charging consumers on thekbasis of higher heating value there remains the need of a device to continuously determine both values to enable manufacturers to control the quality of their product and calculate charges to their customers.

The present invention, therefore, is novel in its provision of means for determining the difierence between the higher and lower heating value of gaseous fuels and which may be used to compensate the lower heating value from calorimeters.

Another object of the present invention is to provide an instrument which is accurate and in which the accuracy of its various components can be easily checked.

An additional obj ect' of the invention is to pro:

2 vid'e an instrument whose indication is dependent only upon the heat values of the fuel.

Another object of our invention is to provide an instrument which will be fully automatic and which will present either a visual indication and/ or a record on a moving paper or other article.

The figure presented represents a schematic view through the principal parts of a calorimeter assembly by which our invention compensates for the high-heat value. of the gas analyzed;

The calorimeter is of the continuous-flow, gaseous, re-heat type comprising a body I having combustion, reheat and heat exchange sections.

.7 Carrier air is supplied through controller 2 which maintains a constant pressure-by having a relay 3 similar to that disclosed in the patent to Gorrie Re. 21,804 magnify pressure variations upon the diaphragm of a standard pressure-reducing valve 4 to maintain the pressure of the air constant.

A constant-volume pump 5, actuated by an electric motor, simultaneously supplies test samples of the gas to be analyzed to the burner 6 in thecombustion section of I and to the burner 1 in a second combustion chamber of our invention. With the gas supply system maintained at a constant temperature sufficiently high above ambient fluctuationsby the pump 5 enclosure,

thermostatically controlled with a simple electric heater, the density of the gas varies as a function ofbarometric pressure which is registered upon the bellows of transducer 8 for compensating the fundamental measuring circuit which forms the subject matter or a ,copending application A ,J. Hornfeck Serial No. 150,850, filed March 21,

to dissipate energy within the box enclosure of pump 5. A thermostat 5B is shown example of a simple temperature sensitive device which can be arranged within the pump 5 en closure for control of a heating device,sueh 5A, through relay 50.

As explained in the Hornfeck application. transducer 8 unbalances a circuit which motor controller ampline'r 9 tends to maintain in balance. While restoring balance through motor (0, amplifier 9 positions voltage divider II which divides the reference voltage of the fundamental circuit of the calorimeter.

The carrier air from pressure controller 2 is heated by the combustion of the sample gas at bu'rr'ier 6 and the temperatures before and after the burner are detected by ther'rno units 12 and I3. The carrier air is then passed in heat eX- The electric heater is shown at 5A :as arranged changing relationship with carrier air continuously entering body I from controller 2 to cool it to a temperature which both streams going to the combustion and reheat sections equal. Then the cooled carrier air is re-heated by heater l l and its temperatures before and after the re-heating are detected by thermo elements l5 and I6.

Of course products of combustion are added in the combustion section which alter the specific heat of the stream going to the reheat section, but with the ratio of carrier air to gas standing at about 500 to 1, the difierence is deemed to alter negligibly the amount of re-heat needed for thermal balance.

The thermo units I2l3l5l6 are made to form the legs of a Wheatstone bridge whose unbalance is detected by motor controller-amplifier I! which then adjusts the electrical power to re-heater M. by having motor l8 position a rheostat [9 in the circuit of heater I4.

The fundamental'measurement is performed by maintaining balance in the circuit of a reference voltage source 29 and the voltage across the heater Id. The unbalance of this circuit is detected by motor'controller-amplifier 22 which simultaneously positions a resistance arm 23 and an indicator 24 through motor 25 and cam 24A. With nothing other than the variation in constituents of the gas to unbalance the fundamental circuit, the final indication by 24 is of the lowheat value of the fuel. Only the lower or net heating value of the fuel is released in the combustion chamber and matched by the re-heater output. The circuit may be calibrated for range of heat values with resistance A and given a suppression of the range with resistance I IA and 23A. With the test gas preheated to a level where its density is unafiected by ambient variations, the cam 24A may be shaped to give the low-heat value of the gas at whatever barometric pressure exists. The barometric pressure variations may be calculated into the circuit, as indicated supra, by positioning resistance arm I I so that it divides the reference voltage of 20, and the final indication of low-heat values will be as of gas at standard, or some predetermined, pressure as well as standard temperature.

Our invention further alters the balance of the fundamental circuit by adding to the voltage across the heater M in proportion to the value of the difference between the higher and lower heating values of the gas. The voltage across the heater at 2! is added to by resistance 26 inserting a portion of the potential of source 21 into the fundamental circuit. Resistance 26 is positioned by motor 28, controlled by motor controller-amplifier 29 sensitive to unbalance in the Wheatstone bridge generally designated at as.

Our invention, then, supplies the additive factor to the lower heating value of the gas, and this is specifically determined in the following manner. 'The sample gas is burned at burner 1 g in combustion chamber 3| which is supplied a carrier air which is dried until its absolute humidity is substantially zero.

The volumes of air and gas are adjusted to raise the humidity of the air resulting from the addition to it of combustion water to the range of a humidity detecting device. The carrier air of the combustion chamber is given a back pressure by adjusting the chamber cover until a flow through chamber 32 results. A hole is provided in this chamber 32 so that the carrier air, with its raised humidity, passes over humidity detector 33.

In the present instance detector 33 is given the characteristics of a well-known type of hotbulb hygrometer called a Dewcel. Essentially the Dewcel comprises two filaments supplied from a source 34 and in circuit completion through a quantity of lithium chloride which allows current passage in the circuit in proportion to the moisture the lithium chloride absorbs. The resulting heat of the completed circuit tends to dry the lithium chloride and prevent current flow so a balance is attained between the humidity of the carrier air passing over the Dewcel and its resulting heat. Thus the Dewcel assumes a temperature which is related to the partial pressure of the water vapor in the air, or the lbs. of water per lb. of dry air. It is, therefore, a measure of the weight of water formed from the combustion of a constant volume of gas, provided the lbs. of dry air furnishedto the combustion chamber do not vary.

Since the difference between the higher and the lower heating value of a gaseous fuel is directly dependent on the quantity of water formed from the combustion of the gas, it is evident that any means whereby the lbs. of water formed per cu. ft. of gas burned can be determined oiiers a means of fixing the difference between the higher and lower heating values.

A leg of Wheatstone bridge 30 is arranged so that it is sensitive to the Dewcel heat and is therefore unbalanced in proportion to the lbs. of water formed per cu. ft. of gas burned.

Should the high-heat compensator have its source 34 disconnected for any substantial length of time, the lithium chloride will absorb moisture to the point that re-application of the source 34 will cause such a high current to flow in the Dewcel circuit that the resulting heat may damage the structure. Consequently, a valve in the form of a conventional tungsten lamp 35 has been found capable of effectively limiting the current until the lithium chloride is dried out to its proper range of resistance.

In the discussion, supra, of the method of arriving at the difference between the high-heat and low-heat values of the gas it was assumed that the lbs. of carrier air furnished per cu. ft. of gas burned would remain constant. Ambient temperature and barometric pressure fluctuations make this impossible. The weight of air flow will vary as the square root of the density, since its flow depends on a differential. However, it is observed that the pressurefluctuations to be normally expected will be small (about 2% max.) and those from temperature about 3% max. Deviations in the gas weight from that at standard vary directly with the density and are found to not exceed .5% of the total heat value of the gas. Thus our invention is practical in operation with the means disclosed controlling all necessary variables.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A calorimeter for gaseous 'combustibles of the continuous flow re-heat type comprising, means for supplying gas at a constant volume rate, means for supplying carrier air at a constant weight rate and absolute humidity of substantially zero, chamber means for burning the combustible in the carrier air, means for detecting the humidity of the carrier air without substantially reducing its humidity, means for pass ing the carrier air over the means for detecting the humidity, a balanceable network including the humidity detector which is unbalanced in accordance with a change in magnitude of the humidity detected, a means sensitive to the unbalance of the network, a means under control of the sensitive means for restoring the balance of the network and simultaneously indicating the rebalanced motion as the difierence between the higher and lower heat values of the gas.

2. An apparatus for giving a response in accordance with the variation between the higher and lower heating values of a gaseous combustible comprising, means for supplying a carrier air at constant weight rate and substantially zero absolute humidity, means for supplying the gaseous combustible at a constant rate, chamber means for combustion of the gaseous combustible in the carrier air, means for detecting the humidity in the carrier air after the combustion without substantial humidity reduction of the carrier air as an indication of the difference between the higher and lower heating value of the gas, means for passing the carrier air over the humidity detector, an electrical network including and unbalanced by the humidity detector, means sensitive to a network unbalance, and means controlled by the sensitive means for giving a mechanical movement in the direction and to the extent of the variation of the difierence between the higher and lower heating value of the gas.

3. Apparatus for giving a response in accordance with the variation between the higher and lower heating value of a gaseous combustible com- 1 prising, means for supplying gas at a constant volume, means for supplying combustion air at constant weight, means for reducing the absolute humidity of the combustion air to approximately zero, a, combustion chamber for the gas and air for the formation of combustion water vapor, a detection chamber for humidity, means for causing flow of the air and combustion water vapor through the detection chamber, a humidity detector whose temperature rise is a known function of the lbs. of water per lb. of air, a Wheatstone bridge network unbalanced by the heat of the humidity detector on one leg, means sensitive to the Wheatstone bridge unbalance, and means controlled by the sensitive means for giving a mechanical movement in the direction and to the extent of the variation of the difierence between the higher and lower heat value of the gas as evidenced by the intensity of the heat of the humidity detector.

4. A continuous flow calorimeter of the gaseous re-heat type including, combustion and re-heat sections joined by a heat exchanger as a body, a means of supplying the sections sequentially with definite volumetric proportions of a gaseous combustible and carrier air, means for maintaining the gas supplied at a level of temperature wherein transient ambient temperature changes will not change its density, an electrical network sensitive to temperatures in the combustion and re-heat sections and unbalanced by a difference in temperature rises of the carrier air through the sections of the body, means for detecting the unbalance of the network, means for dissipating energy input to the re-heat section, means for regulating the input to the re-heat section under the control of said detector, means for indicating and recording the input, a combustion chamber separate from the body, means for supplying the combustion chamber with definite volumetric proportions of the gas and dry carrier air, means for measuring the moisture added to the dry carrier air by the burning of the gas in units common with the re-heat energy, and means for increasing the manifestation of input to the re--heat section by the difference between the higher and lower heating values of the gas as represented by the manifestation of the combustion water produced in the separate combustion chamber.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,997,383 Junkers Apr. 9, 1935 2,026,179 Keith Dec. 31, 1935 2,026,180 Keith Dec. 31, 1935 2,359,278 Allen et al. Oct. 3, 1944 FOREIGN PATENTS Number Country Date 902,952 France Jan. 3, 1945