SU932292A1 - Method of measuring heat consumption - Google Patents

Description

one

The invention relates to methods for measuring the amount of heat imparted per unit of time, liquid or gaseous substances and transported by them in closed circuits, and can be used in testing and research of heat exchangers of low power, in particular transport installations.

A known method for determining the heat consumption is based on measuring the mass or volume flow rate of the coolant and the difference in mean temperatures in the cross sections limiting the heat supply section, i.e., the change in heat content in the heat exchange section. The measurement results are used to calculate the flow rate based on

Q. G C p DT, (.1) where Q is the heat flux (heat consumption);

G - mass flow rate of a liquid or gas (coolant);

Ср - average heat capacity of the heat carrier is related to the temperature range that actually took place; LT is the measured temperature difference between the coolant at the inlet and outlet of the heat exchanging device;

K is a correction factor that takes into account the probable deviations of the true values of the parameters G and dT from the measured values 1.

The disadvantages of the method are: the need for knowledge of the correspondence of the input correction parameters and coefficients to the actual state of the monitored system and the inevitability of errors in measurements associated with the use of a large range of sensors.

Claims (2)

The closest to the proposed method is the measurement of heat consumption, which consists in measuring the difference of 39 temperatures in the flow of heat transfer fluid at the inlet and outlet of this section, further heating the heat transfer medium when it passes the control section with the measurement of the temperature difference at the input and output and in the determination values of heat consumption in a controlled area by the amount of electric power of an additional heater in a control area. By selecting the electric power of the heater so that the EMF of the temperature sensors is the same, the heat flux determined by the coolant in the heat exchanger is determined as a value proportional to the electric power of the heater. Q nQH /. (2) where n is a function of the number of differential thermocouples in both batteries when these quantities are equal, n 1, which will be assumed later for simplicity. The method of measuring the heat consumption is thus 3OMV in that the heat consumption Q is considered a function of magnitude only. The disadvantage of this method is that it is necessary to take into account the change in the parameter Cf with an increase in the average temperature of the coolant at the site of the additional heat source. Supposing that dependence (1) is equally valid for the controlled section (heat exchanger) and the control section of the additional heating zone) and that G const and K const will be obtained, it is obvious that ", (This means that when using the device it is necessary to estimate Q according to (3) and not (2). The value of Cp / Cpn for different substances and temperature ranges can be different. For example, for ethanol, alcohol at a pressure of 10 kg / cm Cp value is kg .2.525 at OS and 0 , EOS, i.e. (CP) (Wed) For water at the saturation line Some increase in the heat capacity ratio is achieved by changing the average temperature from 0 to 2. Thus, using this method requires taking into account information on the thermal properties of the heat transfer media. The purpose of the invention is to improve the accuracy and simplify the process of measuring heat consumption by eliminating information on the thermal characteristics of the heat transfer fluid. the goal is achieved by the fact that the coolant is cooled in the area between the controlled and the control sections to the equality of the averages over the cross section flow temperature of the coolant at the entrance to the controlled and control areas. The drawing shows a scheme for implementing the method. The method is carried out using a closed circuit 1 with a liquid or gaseous coolant moving along it in the direction indicated by the arrow 2. In the direction of flow of the coolant along the circuit there is a controlled area 3 representing a heat exchanger, the heat consumption in which it needs to be measured, the cooler C in which heat is transferred from the coolant in some way, the heat transferred to it in section 3 is heat transferred to it in section 3, the control of the 1st section 5 with an adjustable electric heater 6 and / -wattmeter 7, where it is possible to transfer heat fluids to the coolant, the value of which can be directly measured with a sufficiently small error. Sensors for measuring average cross-sectional temperatures of the flow are located in four sections of the circuit and are combined into measuring circuits 8 and 9 differentially, so that it is possible to register on the secondary measuring instruments 10 differences (differences) of average temperatures at the entrance to the controlled and control sections and at the output of them. The method of measuring the heat consumption is carried out as follows. Along the contour 1, in the direction indicated by arrow 2, the flow of heat transfer fluid is passed and by adjusting the heat removal values in the cooling section k and transferred to the flow in section 5, reach zero temperature differences on the instruments 10 in both their measuring chains 8 and 9, at a thermodynamically steady flow, the heat consumption in the controlled area 3 is determined by the value recorded by the wattmeter 7, regardless of the thermophysical and hydrodynamic characteristics to coolant The proposed method allows direct measurements of heat consumption without calculations (or using equipment performing computational operations) and using information about any characteristics of the coolant. Thus, an increase in measurement accuracy is achieved, in particular, when there is no fully or partially reliable information about the characteristics of the coolant or when these characteristics may be subject to uncontrollable changes in time, for example, in studies of multicomponent coolants, chemically active media, under conditions of incomplete tightness of the circuit etc. The applicability of the proposed method is limited by the values of heat fluxes at which the operation of heat removal and re-supply of heat to the coolant begins to lead to substantial additional energy costs, as well as the values of the coolant velocity at which the average static pressure in the flow in the controlled and control section becomes so different that it turns out to be a noticeable difference in the values of the coolant in these areas. The invention The method of measuring heat consumption by changing the heat content in a liquid or gaseous heat flow detector at the flow determination section; heat, including measuring the temperature difference in the flow of heat transfer fluid at the inlet and outlet of this heat transfer flow, when the control heat passes through it and measuring the temperature difference the input and output and determination of the amount of heat consumption in the controlled area according to the value of the electric power of the additional heater at the control ohm site, characterized in that, in order to improve the accuracy and simplify the measurement process by eliminating information on the thermal characteristics of the coolant, the coolant is cooled in the area between the controlled and control areas until the temperature at the inlet to the controlled and control areas is equal to the cross section of the coolant . Sources of information taken into account during the examination 1. USSR author's certificate h, cl. G 01 K 17/06, 1961. 2. USSR author's certificate ff i 94630, cl. G 01 K 17/10, 1973 (prototype).