SU808924A1 - Calorimetric probe - Google Patents

Description

(54) CALORIMETRIC PROBE

The invention relates to a measuring technique and can be applied in heat engineering works with two-phase dispersed gas-liquid streams with indirect measurement of their phase composition, for example, the expenditure mass concentration of the liquid phase in the stream. A number of devices used in determining the phase state of gas-liquid systems are known: a calorimeter containing a heat-insulated L-shaped case with a conical receiving nozzle, an electric heater, swivel plates, a measuring resistance thermometer, pneumometric tubes flj. However, due to the fact that the measurement of the flow rate of the mixture through the calorimeter is carried out using pneumometric tubes, this calorimeter cannot be used to determine the phase composition in flows with a low velocity (up to 10-15 m / s). With the peculiarities of determining the magnitude of heat loss through the thermal insulation of the housing, this device is not suitable for measurements in unsteady flows (with varying temperature and concentration of the liquid phase). The closest technical solution to the proposed. is a calorimetric probe containing a main heat-insulated measuring channel with an electric heater and a thermal sensor 12. The main disadvantage of this device is the low accuracy of the readings when measuring parameters in clearly pronounced transient processes, for example, at rapidly changing flow temperature and concentration: the liquid phase, and also at sufficiently high (above 10%) concentrations of the x-liquid phase. This disadvantage is due to the fact that with a downstream installation of heaters, the temperature of the sample after the second heating stage exceeds the temperature of the sample after the first stage by the amount of heating of the sample in the second stage. This difference in temperature is the higher, the greater the concentration of the liquid phase in the stream under study, which is explained by the large expenditure of heat for the evaporation of the liquid. As a result, heat losses through the thermal insulation and the internal walls of the calorimeter, determined by differences in temperature, become clearly dependent on the concentration of the liquid phase in the flow, which limits the upper limit (10-12%) of the range of measured concentrations of the liquid phase and also impairs the operation of the device under unsteady conditions. The reduction of heat losses by increasing the thickness of the thermal insulation is unacceptable, since it increases the inertia of the device, due to the heat capacity of the body of the calorimeter

The purpose of the invention is to improve the accuracy of measurements in non-stationary conditions.

This goal is achieved due to the fact that in the calorimetric probe containing the main heat-insulated measuring channel with electric heater and thermal sensor, parallel to the main channel, an additional measuring channel equipped with electric heater and thermal sensor is installed at the inlet, in which also installed a temperature sensor.

The drawing shows the proposed calorimetric probe.

The probe contains a two-channel Y-shaped case 1 with an evaporative f-core) 2 and an overheating (optional) 3 measuring channels and an output mixing channel 4 made of, for example, quartz glass with asbestos heat insulation, and is a combination of channels 2 and 3. Inside evaporative 2 and superheating 3 channels, which are made parallel, placed heaters 5, for example electric, in the form of a frameless spiral. At the entrance to the evaporating channel 2 there is a conic receiving nozzle of a vapor-liquid mixture; at the entrance to the superheating channel 3 there are 3 separating nozzles 7 of inertial type. Inside each of the channels directly behind the heaters 5, as well as in the mixing channel 4, mustache. Smoothed grids 8 for aligning the parameters of the mixture passing through the channels through the channel sections, directly behind the grids 8, thermocouple thermocouples 9,10 and 11 are placed inside each channel. The necessary conditions of the instrument are continuous passage of the selected flow through the instrument channels , measuring the temperature of the test flow, as well as the orientation of the receiving nozzle of the vapor-liquid mixture 6 according to the flow. The latter condition follows from the fact that in order to achieve the same coningration of the liquid phase in the main flow and the main measuring channel of the device,

and the more inertial liquid phase of the flow must enter the evaporating channel of the device 2 if possible without settling. Ia walls of the receiving nozzle The probe works as follows. The device is installed in flow according to the above catches, taken from the flow for the difference in pressure at the inlet and outlet | sample of the mixture is divided into two parts. One of them passes through the evaporation channel 2. On the heater 5 of the specified channel 2 the sample evaporates. and overheating of the produced gas, measured by thermocouple 9. The temperature tg must exceed the temperature of the test stream t (, by 5-30. The lower limit () of the specified range is determined by the need for complete evaporation of the liquid phase, the upper one - (30 ) is set to prevent excessive overheating of a part of the sample in the superheater channel 3. At high concentrations of the liquid phase. The gas obtained after heating passes through the grid 8, where it is mixed and temperature controlled across the channel section. The second part of the sample passes through the separator 7 nozzle obtained After separation of the liquid, the gas enters the superheater channel 3, where it is heated, as measured by thermocouple 10, the temperature in any operating mode must exceed the temperature. gas at the outlet from the evaporative channel tg within 10-15, which is necessary to more accurately determine the flow ratio through the channels of the device. With the passage of superheated gas through the grid 8 installed in the mixing channel 4, both parts of the sample are mixed, and the sample temperature t is recorded by the measuring thermocouple 11. Mixing both parts of the sample and determining the mixing temperature is necessary to determine the ratio, flow through the evaporation and superheating channels device.

The mass flow rate concentration of the liquid phase in the flow, which is an output parameter and an object of indirect measurement, is calculated based on the calorimeter heat balance equation using the following formula: V k (tip -trt) - (tfl-tn) r / Cp + tw -

N "NU

t - tg

where kj

t;

 40 f 1

and N are the capacities of electric heaters, respectively, in the evaporative 2 and overheated 3 channels, the value

N,

Claims (2)

for this device is constant; k is the calorimeter calibration coefficient; tf, is the temperature of the flow under test; temperatures measured by thermocouples, respectively 9, 10 and 11; g is the specific heat of vapor formation of a liquid; Cp is the gas heat capacity. phases; tj is the boiling point of the liquid phase. In the above formula, t, tg, and t are the measured values, the values of g, Cp, and ts are the thermophysical parameters of the medium, reference data. Calibration coefficient k (tt) taking into account the ratio of heat losses through the thermal insulation of the calorimeter channels and depending only on the temperature differences inside the instrument channels and the flow washing it, is determined by calibrating the calorimeter in a single-phase medium, for example, gas 0 Due to the fact that in the proposed device, the sample taken is heated in two parallel channels (heating stages), the temperature of the sample parts in the evaporating 2 and superheating 3 channels differ slightly. The required inputs for the sample taken lead to the fact that when the concentration of the liquid phase in the test flow is changed, the composition of the hydraulic resistance of the evaporation channel 2 due to evaporation of the liquid changes, while the hydraulic resistance of the superheating channel 3 remains unchanged. the ratio of costs of the parts, the sample through the evaporation and superheating channels, which stabilizes the temperature difference between the parts of the sample -t at the outlet of the superheating 3 and evaporating 2 channels. These factors lead to the equalization and stabilization of heat losses through the heat insulation of the housing and the production of little varying loss factors in the system of heat balance equations taken into account by the coefficient k, which allows the instrument to be calibrated in a single-phase gaseous medium. Stabilizing the temperature difference within 10-15 and leveling the heat loss through the walls of the evaporating 2 and superheating 3 channels reduce the thickness of the thermal insulation of the housing 1, which leads to a decrease in the inertia of the calorimeter, which allows by moving the receiving nozzle 6 across the section of the flow being flowed, for example by moving or turning the instrument, measure the concentration distribution of the liquid phase. The proposed device is characterized by low inertia and allows, by measuring a small number of parameters (temperatures t, t ,, and t), to calculate the mass concentration of the liquid phase in the flow with an error not exceeding 0.5% (an error of 0.5% was obtained by testing the calorimeter in dispersed gas-liquid flow of nitrogen in the temperature range from (h-50 ° C) to (-200 C) and the weight concentration of liquid nitrogen 0-40%). Claims Calorimetric probe containing a main heat-insulated measuring channel with an electric heater and a thermal sensor, characterized in that, in order to improve measurement accuracy under non-stationary conditions, an additional measuring channel equipped with a separation heater and a thermal sensor is installed at the inlet combined into a mixing channel, which also has a temperature sensor. Sources of information taken into account in the examination 1.Kirillov I.I., Ziegler Kh.Kh., Fadeev I.P. The application of an electrocalorimetric method for measuring humidity in a stream of wet steam. Works CKTI, vol. 65, 1966, 0.7-10. 2. Kirillov I.I. and others. Electrocalorimetric method for determining the weight degree of moisture content of water vapor. Works CKTI, vol. 65, 1966, p. 11-16 (PROTOTYPE). Fun eleven output