JPH06100510B2 - Calorimeter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a calorimeter, and more particularly, to a layer flowmeter under the condition that a thermal type flowmeter and a laminar flowmeter are connected in series to keep the output of the thermal type flowmeter constant. The present invention relates to a simple calorimeter for mixed fuel gas, which measures the calorific value of the mixed fuel gas obtained as a function of the pressure loss by detecting the pressure loss of the flow meter.

Prior art Fuel gas and natural gas are legally stipulated to detect and record the amount of heat and combustibility at the time of manufacturing and shipping, and a calorimeter for measuring the amount of heat of a mixed gas is stipulated based on this rule. There is. A typical calorimeter is the Junkers-type running water calorimeter. The principle of this calorimeter is that the fuel of the mixed gas is completely combusted with the air, the waste gas generated by combustion is cooled to the initial gas temperature, the generated steam is condensed, and the total amount of heat generated is stored in the calorimeter. By absorbing it in flowing water, the amount of flowing water corresponding to a certain mixed gas sample,
The total amount of heat is obtained by multiplying the temperature difference of the warm air at the inflow port and the outflow port of the flowing water and from the multiplication result.
This calorimeter is used as a reference calorimeter, but in the test, the temperature difference between the water temperature and room temperature should be matched within a range of ± 0.5 ° C, or the temperature change of water during one measurement time It is suitable for precision tests because it is strict in the measurement environment such as keeping it within 0.05 ° C and the response of the measurement is poor, but it is not suitable for the production line. It is also permitted to use a calorimeter, and the calorific value is usually measured continuously by a quick response calorimeter. The quick response calorimeter calculates the fuel gas and air by a flow meter, mixes them, burns them with a burner, and burns them with the temperature of the exhaust gas produced by burning and the temperature of the combustion air at the burner inlet. Each temperature difference is detected by detecting with a temperature detector such as a thermocouple, while detecting the specific gravity of the fuel gas with respect to the air, and the total calorific value of the sample gas,
The Woppe index (referred to as WI), which is the ratio of the specific gravity of the sample gas to the air, is calculated, and the calorific value of the test fuel gas is calculated as the product of WI and the square root of the specific gravity of the sample gas to the air. . As another method of detecting the amount of heat, it has been experimentally confirmed that the amount of heat of the mixed gas is proportional to the density of the mixed gas, and it has been attempted to calculate the amount of heat from the density measurement result of the mixed gas.

Problems of the conventional technology The quick-response calorimeter described above is a practical calorimeter that replaces the Conkers-type running-water calorimeter, which is a highly accurate reference calorimeter, but its measurement value drifts, resulting in low measurement accuracy. The measurement value is corrected by comparing the value with the Junkers-type running water calorimeter at a rate of twice in one continuous operation time. This correction operation is troublesome, and in the method of detecting the density, there is a problem that the density meter is usually expensive, and it is not possible to easily and inexpensively obtain the calorific value.

Means for Solving Problems The present invention has been made to solve the problems of the above-mentioned conventional calorific value measuring means, and the physical quantity of the mixed gas is that the calorific value is proportional to the density, the constant pressure specific heat and the viscosity are inversely proportional. The purpose of this is to provide a simple and accurate calorimeter by applying the flow rate measurement principle of each of the thermal type flow meter and the laminar flow meter, and the main point is that the fuel gas is A thermal type flow meter that detects the mass flow rate of the fuel gas from the temperature difference in the upstream and downstream of the resistance wire wound around the flow tube and the heating means that heats with a constant current flowing in a laminar flow, and flows between both ends of the laminar flow element Difference between the laminar flow elements in the laminar flow meter connected in series with a laminar flow meter that detects a volumetric flow rate proportional to the pressure difference of the fuel gas The pressure is detected and the heat quantity of the fuel gas is inversely proportional to the differential pressure. A calorimeter to be calculated as a quantity is submitted.

Example The fuel gas currently used as city gas is a liquefied natural gas (hereinafter simply referred to as LNG) as a base gas, and is mixed with a hydrocarbon gas having a high calorific value such as propane and butane in order to obtain a predetermined calorific value. . Although LNG has methane as a main component, the amount of methane and the amount of heat, which are different depending on each production area, therefore, the distribution amount of propane and butane gas mixed with LNG in each production area is determined. The relationship between the heat quantity and density ρ, the constant pressure specific heat Cp (hereinafter simply referred to as specific heat) and the viscosity μ with respect to these mixed gases is the density ρ with the heat quantity as the horizontal axis,
FIG. 3 shows an example of the measured values with the specific heat Cp and viscosity μ plotted on the vertical axis. That is, the heat quantity of the mixed gas is proportional to the density,
There is a relationship that is inversely proportional to viscosity. On the other hand, in FIG.
In the figure, 50 is a flow tube with excellent thermal conductivity. In the figure, 50 is a flow tube with excellent thermal conductivity. Density ρ from the arrow direction, fluid such as fuel gas with specific heat Cp is Q, Reynolds number is 200 or less. It is distributed in a laminar flow. Reference numeral 51 is a heater composed of a resistance wire wound around the center of the flow tube 50, and is heated by terminals 51a and 51b with constant power. 52 and 53 are resistance wires which wind the flow tube 50 in the front-back flow of the heater 51, respectively, and have the same resistance value when the flow rate Q = 0, and change the resistance value due to the flow. Obtained from a bridge circuit with two sides of each bridge. The terminals 52a, 53a, 53b are terminals of a bridge circuit (not shown). Since the heat conduction from the tube wall of the flow tube 50 of the thermal flow meter having such a configuration to the fluid is performed through the laminar boundary layer of the fluid and is proportional to the thickness of the laminar boundary layer, the bridge It is known that the output V has a relationship of V = K ₁ ρCpQ (1) where K ₁ is a proportional constant. For a fluid having a known specific heat Cp, an output V proportional to the mass flow rate ρQ can be obtained. . Also,
FIG. 5 shows a known laminar flow meter in which a laminar flow rate Q flows in a flow tube 60 having a radius r and a length l, and 61 is a pressure difference Δ.
It is a laminar flow element for generating P, and is composed of a thin tube or a lattice. The pressure difference ΔP measured by the differential pressure gauge 7 as the inflow pressure P ₁ and the outflow pressure P ₂ is Hagen-Poiseuille's equation when the fluid is a gas of viscosity μ, and the flow rate Q is It is represented by. When the inflow pressure P ₁ is high and the differential pressure ΔP is low in the equation (2), (P ₁ + P ₂ ) / P ₁ ≈2 may be used, and the flow rate Q is obtained in proportion to the differential pressure ΔP.

The calorimeter of the present invention has a relational expression (1) between the thermal flow meter and the laminar flow meter as described above, in which the thermal flow meter and the laminar flow meter are connected in series and the fuel gas is circulated at the same flow rate output. ),
The amount of heat is obtained from the equation (2) and the relationship between the physical properties of the fuel gas and the amount of heat shown in FIG. The relationships shown in FIG. 3 represent the following (a), (b), and (c).

(A) From the relationship between the fuel gas density ρ and the heat quantity H ρ = K ₂ H (K ₂ : constant) …… (3) (b) From the relationship between the fuel gas specific heat Cp and the heat quantity H Cp = K ₃ / H (K ₃ : constant) (4) (c) From the relationship between the fuel gas viscosity μ and the heat quantity H μ = K ₄ / H (5) That is, the above (3), (4), (5) Shows the formula.

Substituting equations (3) and (4) into equation (1), V = K ₁ K ₂ K ₃ Q = K ₅ Q (6) However, K ₁ K ₂ K ₃ = K ₅ (2) The expression is (P ₁ + P ₂ ) / P ₁ = 2, and when the expression (5) is substituted, By substituting the equation (7) into the equation (6) and expressing the constant by K while keeping the output V constant, the following equation (8) is obtained. Is required. That is, the heat quantity H of the fuel gas can be calculated as a relationship inversely proportional to the differential pressure ΔP.

FIG. 1 shows the configuration of a calorimeter of the present invention that embodies the above principle. In the figure, 1 is a flow path through which the fuel gas to be measured flows, 2 is a pressure reducing valve for reducing the pressure of the fuel gas to a constant pressure, 3 is a filter, 4 is a pressure gauge, 12 is an adiabatic tank, 5, 6,
Reference numeral 7 denotes each of the above-mentioned thermal type flow meter, laminar flow meter and differential pressure meter housed in the heat insulation tank, which is based on the above-mentioned principle. Reference numeral 8 denotes a flow rate setting control device that sets the flow rate output of the thermal type flow meter 5 to a constant value, and sets the flow rate output in percentage with the maximum flow rate as 100%, and controls to the set flow rate. Reference numeral 10 is a temperature measuring element for measuring the temperature in the heat insulating tank 12, 9 is a calculator for calculating the heat quantity based on the temperature measured value of the temperature measuring body 10 and the differential pressure ΔP signal, and the calculation result is the heat quantity display 11 Is displayed. The flow path 1a portion in the heat insulating tank 12 is formed by winding the flow path 1 in a coil shape in order to remove strain due to the heat effect of the flow path 1. FIG. 1 shows a specific example for implementing the equation (8). The temperature measuring element 10 has a constant mass flow rate when the output of the thermal type flow meter 5 is constant. This is for correcting the difference between the volume flow rate Q and the flow rate Q of the laminar flow meter in the mass flow rate, and the temperature measuring element 10 can be removed by controlling the temperature inside the adiabatic tank 12 constant.

FIG. 2 shows another embodiment, in which FIG.
The same components as those in the figure are designated by the same reference numerals as those in FIG. 1 and their explanations are omitted. 105 is a well-known bypass type thermal flow meter in which the thermal flow meter 5 and the laminar flow meter 6 in FIG. 1 are integrated, and the principle structure of the bypass type thermal flow meter shown in FIG. Is to have. In FIG. 6, reference numeral 600 denotes a mainstream pipe through which fuel gas flows, and a laminar flow element 610 is fitted in the center of the mainstream pipe. Reference numeral 500 denotes a bypass pipe that opens in the laminar flow element 610 of the main flow pipe 600 and the pipe walls 501 and 502 in the front and rear flow parts.
Is a heater 51 and resistance wires 52, 5 in the thermal type flow meter of FIG.
3 is wound to form a bypass type thermal flow rate. The resistors R ₁ and R ₂ are resistors that form two sides of a bridge composed of the resistance lines 52 and 53, and E is a power source applied to the bridge.
The bridge circuit output measures the mass flow rate of the bypass pipe 500 as described above. However, since the flow in the bypass pipe 500 and the main flow pipe 600 are both laminar flow, the mass flow rate of the main flow pipe 600 is the bypass pipe. It is determined by detecting the mass flow rate of 500. That is, the flow pipe flow rate flowing in a laminar flow with a constant differential pressure is in inverse proportion to the flow pipe resistance, and the resistances in the bypass pipe 500 and the main flow pipe 600 are known in advance. Therefore, also in the case of the bypass type thermal type flow meter, if the flow rate output V of the bypass pipe 500 is made constant, the equation (8) can be applied, and the heat quantity H of the fuel gas can be obtained from the relationship inversely proportional to the differential pressure ΔP. Returning to FIG. 2, 100 is a well-known control valve for controlling the flow rate of the thermal type flow meter 105 by comparing the output of the thermal type flow meter 105 with a set value, and controlling the output constant. Show. In FIG. 7, reference numeral 102 denotes a coil driven by a current according to a comparison signal of the flow rate setting control device 80, which is housed in a casing 101 having a yoke 103, and has a fuel gas flow rate Q of 600a,
The valve 104a that cooperates with the valve seat 106 that is provided with the valve hole 106a that is divided into 600b is electromagnetically driven. The valve 104a is elastically supported by the leaf spring 105, and is integrally configured with the plunger 104 that receives an electromagnetic force according to the exciting current of the coil 102. The plunger 104 is subjected to a displacement in which the electromagnetic force acting on the plunger 104 and the elastic force of the leaf spring 105 are in parallel with each other. As described above, in the embodiment of FIG. 2, the bypass type thermal type flow meter 105, the control valve 100 and the flow rate setting control device 80 perform the calculation satisfying the equation (8). Also in this case, the heat insulating tank 12 may be a constant temperature tank. or,
In FIG. 6, the laminar flow element 610 of the thermal type flow meter is a blocking plate that closes the flow path, and only the thin tube 500 may be used. Although the bypass type thermal flow meter 105 and the control valve 100 are separated in the drawing, they may be integrated. Also, (1)
If the flow meter is a thermal type flow meter that satisfies the relational expression of the equations, then FIG.
It is not necessary to use the thermal type flow meter shown in the figure.

Effect According to the calorimeter of the present invention as described above, the calorific value of the mixed fuel gas can be measured with high accuracy by an extremely simple means. Further, since the temperature change in the heat insulation tank is small, a stable amount of heat can be obtained, and it is possible to inexpensively provide auxiliary means for the reference calorimeter as a simple calorimeter.

[Brief description of drawings]

FIG. 1 is a configuration example showing an embodiment of a calorimeter according to the present invention, FIG. 2 is a configuration example showing another embodiment, and FIG. 3 is a diagram showing a relationship between physical properties of fuel gas and heat amount. , FIG. 4 is a principle diagram of a thermal type flow meter, FIG. 5 is a principle diagram of a laminar flow meter, and FIG.
FIG. 7 is a principle diagram of a bypass type thermal type flow meter, and FIG. 7 is a principle diagram of a control valve. 1 ... flow path, 5,105 ... thermal type flow meter, 6 ... laminar flow meter, 8 ... flow rate setting control device, 9 ... calculator, 10 ... temperature sensor, 11 ... calorific value display, 12 ... Insulation tank.

Claims (4)

[Claims] 1. A thermal type flow meter for detecting a mass flow rate of fuel gas from a temperature difference in a front and rear flow of a resistance wire wound around a flow tube which circulates fuel gas in a laminar flow and a heating means for heating with a constant electric power. , A laminar flow meter that detects a volumetric flow rate proportional to the pressure difference of the fuel gas flowing between both ends of the laminar flow element is connected in series,
A differential pressure between laminar flow elements in the laminar flow meter obtained by keeping the temperature difference of the thermal type flow meter constant is detected, and the heat quantity of the fuel gas is calculated as an amount inversely proportional to the differential pressure. Calorimeter to do. 2. A main pipe having a laminar flow element interposed between the main pipe and a thin pipe which opens in the main pipe wall sandwiching the laminar flow device and forms a bypass flow path of the main pipe, a heating means for heating the thin pipe, and the heating. A thermal type flow meter for detecting a mass flow rate of the fuel gas flowing through the main pipe, and a temperature difference detecting means for obtaining a temperature difference between the upstream and downstream of the heating means of the fluid obtained by being heated by the means, A temperature difference signal of the thermal type flow meter, which comprises a control valve including a driving means for displacement driving in proportion to the previous temperature difference in the flow meter and valve means for opening and closing the flow path in association with the driving means. And a reference voltage, and based on the comparison value, the heat quantity of the fuel gas in the mass flow controller for controlling the driving means of the control valve to the flow rate output in which the fuel gas flow rate is set to the reference voltage. The amount is inversely proportional to the pressure difference between the laminar flow elements in the main tube. Calorimeter according to claim 1, wherein the calculating the fuel gas heat. 3. The calorimeter according to claim 1, wherein the thermal type flow meter and the laminar flow meter are housed in a greenhouse and the specific heat of the fuel gas is corrected based on the temperature in the greenhouse. 4. A calorimeter according to claim 1, wherein the thermal type flow meter and the laminar flow meter are housed in a constant temperature bath which maintains a set constant ambient temperature.