SU885830A1 - Calorimeter - Google Patents

Description

(54) CALORIMETER

one

The invention relates to the measurement of the heat released during fast processes, such as combustion, dissolution, etc.

Known calorimeter type Calvet integrating heat flux 1.

The main disadvantage of such a calorimeter is the greater complexity and duration of measurements.

The closest to the proposed technical essence and the achieved result is a calorimeter containing a calorimetric bomb, a central-hygienic unit, a thermostat and a measuring thermopile. In this calorimeter, the heat released in the bomb enters the massive metal block through a thermopile that evenly surrounds the bomb. The thermo-emf signal, proportional to the heat flux, from the bomb enters the integrator, whose readings are proportional to the measured t% raft 12.

The disadvantage of such a calorimeter is a decrease in accuracy when measuring large heats, exceeding 30-50 kJ, when the calorimetric bomb overheating exceeds the value. In addition, the unit overheats

leads to delayed measurements, since one has to wait until the block has cooled to the initial temperature of the experiment in order to start the next one.

The purpose of the invention is to expand the range and reduce the measurement time.

The goal is achieved by the fact that the central unit is equipped with an cooling system and a temperature sensor connected to the input of the thermostat, the output of which is connected to the integrator's input and the cooling system through the switches.

15

On the outer surface of the central unit, grooves are made with a measuring thermopile disposed therein, over which a shell is installed comprising a heater, a temperature sensor and a cooling system.

FIG. 1 is a block diagram of a calorimeter; FIG. 2 - equivalent calorimeter circuit using electroshackle analogies; on

25 of FIG. 3 - curves explaining measurements.

Claims (2)

The calorimeter (Fig. 1) consists of a calorimetric bomb 1 with the test substance, a central unit 2, 30 measuring thermopile 3, a shell 4 in which temperature sensors, heater and cooler, amplifier 5, integrator b, thermostat 7, switch 8 are placed and valve 9. The calorimeter operates as follows. The initial temperature of the calorimeter is kept constant due to the operation of the thermostat circuit 7 with the temperature sensor and the shell heater 4, the contacts of the switch 8 are closed, the valve 9 is closed. When heat is released, the temperature of the bomb 1 and the central unit 2 rotates, the signal from the thermopile 3 enters through the amplifier 5 to the integrator. The temperature increase of the central unit and the shell 4 by means of the thermostat 7 causes the valve 9 to open, which leads to the cooling of the shell 4 After the temperature of unit 2 reaches the initial temperature, the thermostat 7 closes valve 9 and turns off the integrator 6 by switch 8, thus ending the measurement. The operation of a caloimeter can be carried out using the electrothermal analogy method. The calorimeter can be represented by an equivalent circuit (Fig. 2) in which capacitance C corresponds to the heat of the Xorometric bomb, the resistor R is equivalent to the thermal resistance of the measuring layer, the EO source to the calorimeter cooler, the position I of the switch S corresponds to the case when the central unit maintains isothermal conditions measurement, position II of the case when the calorimeter is cooled. When determining the heat, the area under the curve 0 (Fig, 3), which is equal to Uo -t / Rc Q, is IWl.) Dt -irJe dt-UoC о When determining the heat during cooling of the calorimeter, determine the area under the curve cG up to the point in time before the bomb reaches the initial temperature (the temperature of the bomb corresponds to the voltage on the capacitor Uc (t) curve b), that is, to the point in time trt (Udt R о®) Thus, if the integrator is turned on before time t, his readings correspond to the desired heat. The application of the proposed calorimeter allows to expand the range of variable heat from 30 to 400 kJ and halve the measurement time. Invention 1. A calorimeter containing a calorimetric bomb, a central unit, a thermostat and a measuring thermopile connected through an amplifier to an integrator, has a mass of that, in order to expand the range and shorten the measurement time, the central unit is equipped with a cooling system and a temperature sensor connected to the input of the thermostat, the output of which is connected via switches to the integrator input and the cooling system. 2. A calorimeter according to claim 1, characterized in that on the outer surface of the central unit there are grooves with a measuring thermocouple placed in them, on top of which there is a shell containing a heater, a temperature sensor and a cooling system. Sources of information taken into account in the examination 1. Oleinik B, N. Accurate calorimetry. M., Standards, 1964 2.Galperin L.N. and others. - Physical Chemistry, 51, 1256, 1977, p. 80-83 (prototype).