CS215512B1 - Method of determination of the light quantity - Google Patents

Description

(54) Method of determining the amount of heat

The invention relates to a method for determining the amount of heat transferred in a heat exchanger through a mass.

Judge known; The methods of determining the amount of heat flowing through the mass ⁵ determine the amount of heat from the amount. flowing mass and temperature difference before and after the exchanger. The amount of flowing mass ⁵ is determined; mechanical, mostly rotating meters. In particular, the mechanical parts of the known meters are material and quality-intensive and cause frequent equipment failures, especially when the flow velocity of the flowing material is low or too high.

Above; these shortcomings are; They are removed by the method of determining the amount of heat Q according to the invention, which is characterized in that between inlet and outlet; a current is formed; thermally conductive; connections from; of matter is * which. thermal conductivity is at least ⁵ 1 order higher than thermal conductivity of other materials! and the weight connecting thermally conductively ⁵ inlet and outlet stream and the. measured temperatures and arrangement properties, se; calculates; amount. Q passed-warm.

K. calculations can be made; use, for example, the following; equations / (where at least three & t1, t2, t3, t4 " t ", te are: measured Jt

T2 f

τι or ti — I2

—3 — Ϊ5. (t3-t6). A - (ti-ta)

As dr

T2

Q = f · (to-16). B- (tl-12)

Tl

Other temperatures needed to quantify the relation for the amount of heat Q are determined by the relations:

\ s dr. (t3-15) - (U — te).

t5 - (- tS___ t5 -) - t5

2 t4 ~) ~ t6 .__ A2A3__ 'A2A3 + A1A3 + A2A1 ti - or ti ~ t'2 ~ or t2 = 14 + t6 _ t4 - (- t6 ”2 ..... ~~ * 2 t4-j- t6 t4 + t6 “~ 2 ~ l t3-l ~ t5 ts - [- t5 ~ 2 ~ 2 or can be determined by measurement.

The measured temperature t1 is measured at the thermally conductive connection 5 of the inlet and outlet of the mass stream, closer to the inlet mass flow, the measured temperature t2 is measured at the thermally conductive connection 5 of the inlet and outlet mass stream, closer to the outlet flow of the mass. measured in the supply current. 1 mass, in the direction of mass movement, before. by connecting the thermally conductive connection 5 of the inlet and outlet of the mass stream, the measured temperature t1 is measured in the mass outlet stream 4, in the direction of the mass flow, after the connection of the thermally conductive connection 5 of the inlet and outlet. of the mass flow, the measured temperature I5 is measured in the mass inlet stream 2, between the thermally conductive connection 5 of the inlet and outlet mass flow and the heat exchanger 6. The measured temperature te is measured in the mass flow stream 3 between the heat exchanger B and the connection thermally conductive ^one connection 5 inlet and outlet stream of material, a is the ratio between the current density of the entire mass flow and a current density portion of the supply current, it is connected to heat conducting connection 5 inlet and outlet stream of material, B is the ratio between the current density of the entire mass flow and the current density of a portion of the drain stream to which the thermally conductive connection 5 of the inlet and outlet streams of the mass is connected. Ai is the thermal conductivity between the mass supply stream and the location on the thermally conductive connection 5 of the mass supply and exhaust stream, at t5-Ht5. __ A1A2 + A1A3 'A1A2 + A1A3-I-A2A3 t5-j-t5 .__ Λ1Λ2 ___' Α2Α34Ά1Α34Ά2Α1

14 ~ pt6. Kterémί Δ3-ΑΆ2 As' Α1Λ2 I -Ai As I Α2Λ3 where temperature ti is determined, A2 is the thermal conductivity of the part of the thermally conductive connection 5 of the inlet and outlet mass flow between the places where temperatures ti and t2 are determined at the thermally conductive connection 5 of the inlet and outlet of the mass stream, in which the temperature Ϊ2 is determined and between the mass flow stream, the thermal conductivities Ai and As. they also respect the thermal resistance when transferring heat from the flowing mass to the thermally conductive connection of the inlet and outlet mass flows and vice versa, and the thermal conductivity Ai, As, As are directly proportional to the thermal conductivity coefficient and cross-sectional area of the masses inversely proportional to the lengths of the respective sections of this junction 5 and wherein further τι is the beginning and T2 the end of the period in which the amount of heat Q is transmitted and dr is the time differential.

The ratios A, B and the conductivity Ai, As and As can be calculated or measured.

Since it is not necessary to measure the current density of the mass flow by mechanical sensors to determine the amount of heat Q, but this is determined indirectly by means of temperatures, the need for material-intensive and failure devices is eliminated. differently measured time variables - movement and temperature difference. The determination of the amount of heat transferred from the measured temperatures makes it possible to easily process the measured data, especially when using electrical sensors such as thermocouples, thermistors and temperature-dependent resistors, and partial or complete electronic processing of the measured temperature data. At least an approximate determination of the amount of heat transferred can often be carried out on existing inlets to the heat exchangers without interrupting them and without interrupting the operation of the exchanger. The most suitable material for making the thermally conductive connection is copper. ..

The drawings show two cases of an arrangement for determining the amount of heat transferred according to the invention. Fig. 1 is an arrangement diagram feasible on existing three-temperature heat exchanger inlets; and Fig. 2 is a branch diagram with a branched mass flow that allows more accurate temperature difference measurements.

An example of a particular embodiment of the invention

In the supply line (Fig. 6) to the heat exchanger 6, which is the heater in the room, a vertical flow divider of polyvinyl chloride, having less thermal conductivity than metals, is inserted in the vertical part of the pipeline with respect to fouling and accumulation of air bubbles. The mass flow divider divides the mass flow into ten equal partial streams flowing through ten centrally symmetrically spaced channels of equal cross-section.The inner wall of one of the channels is formed by a copper pipe connected to a copper rod of the thermally conductive connection 5 of the feed stream 1 and 2. The thermistor 7 measures the temperature ts, the thermistor 8 measures the temperature ts, the thermistors 10 and the temperature t1 and t, and the thermistor 9 the temperature t6.

In order to increase the accuracy of the measurements, in addition to the temperatures ti, tz, t3, ts and te, the temperature differences (ti — tzj, (t3–16), (tS – 15) are calculated directly in the differential connection.

A = 10, B = 1, A ₂ = 2.8644 W / K.

The following temperatures and temperature differences were measured:

t 1 = 76.5 ° C t 2 = 73.6 ° C t 3 = 81.2 ° C ts = 80.3 ° C te = 58.9 ° C t 1 = t 2 = 2.931 ° C t 3 = te = 22.37 ° [.Alpha.] D @ 25 = 0.926 DEG

Using the relationship between temperatures, t4 = 58.9926 ° C is determined

Instantaneous values are calculated from other relationships

Ai = 1.9545 W / K;

A3 = 0.5666 W / K.

By quantifying the relation for the amount of Q transferred heat for 0.5 hours = 1800 s, we find Q = 3.636 MWs. The quantity found differs by 3% from the quantity determined by a more accurate measurement method.

The invention can be used to determine the amount of heat transferred wherever the current density of the heat transfer mass does not change in the heat exchanger, for example in central heat exchangers of buildings.

Claims (1)

Subject Method for determining the amount of heat transferred by a flowing mass in an exchanger, in which only the temperatures of the inlet and outlet streams of the mass and the thermally conductive connection are measured, characterized in that a thermally conductive connection is formed between the inlet and outlet streams. OF THE INVENTION the conductivity is at least 1 order higher than the thermal conductivity of the other materials and masses connecting the thermally conductive inlet and outlet stream, and the amount of heat transferred is calculated from the measured temperatures and configuration properties.