LT4115B - A differential method for measuring of a heat - Google Patents

Abstract

Invention belongs to the domain of heat metering. Using this differential heat metering method, the quantity of consumed heat is defined according to the differential between the heat supplied to the customer and that returned from the customer. The main point of the invention is that the differential between the supplied heat and returning heat is determined by temperature differences in different points of the conductor. The heat conductor is a rod with an equal cross-section. One end of this rod is heated with the supplied heat and the other end is heated with the returning heat. Basically the conditions of heat transfer to the heat conductor are the same in the both heated ends. The constant coefficient of the measuring method is derived using experimental or mathematical method. This coefficient is multiplied by the metered temperature difference. The product is integrated. The integrator indicates the amount of the consumed heat.

Description

The invention relates to the field of heat measuring technique.

A known analog of the invention is the invention "Thermal Compensation Heat Measurement Method" (LT Patent No. 3169), which describes a method for measuring the amount of heat consumed by a heat sink.

The general features of the analog of the invention and the present invention are as follows:

1. A known proportion of the total heat flux shall be used for the measurements.

2. The result of the measurement shall be obtained by using a known multiplication factor of 10.

In the analog of the invention, the result is obtained by compensating a known part of the heat returning from the heat sink to the amount of heat of the same part known to the heat sink. The amount of compensated energy measured, multiplied by a known factor, determines the amount of heat consumed by the heat sink. An additional source of electricity is used for measurement purposes.

The present invention seeks to disclose a new way of measuring heat consumption by a heat sink. The implementation of the invention will simplify the production of heat meters and reduce the cost of devices manufactured according to the invention.

The essential and, in all cases, sufficient features of the present invention are as follows:

1. For measurement purposes, a known fraction of the heat flow to and from the heat exchanger shall be used.

2. These isolated parts of the heat flux are subjected to a measuring element to determine the difference in heat of these parts.

3. The measuring element may be a heat-conducting rod connecting the feed and return heat transfer tubes.

Another variant of the measuring element consists of a system of two vessels connected by a closed loop. The system is filled with the heat transfer medium of the measuring system. The vessels are mounted on the supply and return heat transfer pipes. The heat transfer rate of the measuring system describes the amount of heat consumed by the heat sink.

4. The heat difference obtained shall be multiplied by the known factor and the heat consumption of the sampler shall be obtained.

The present invention differs from the known analog in that:

1. The heat carried by both heat flows (supply and return) is used.

2. A measuring element that does not require an additional power source is used.

3. The measurement shall be made directly on the measuring element and shall not require the measurement of compensating energy.

The supplied heat flux Q _p (see diagram) from heat source 1 in pipe 4 is divided into two streams: heat flux Qj is transmitted to heat sampler 3 and heat flux qi is transmitted to measuring element 2. The amount of heat Q _o consumed by heat sampler 3. The heat flux Ch from the heat sink is divided into two flows: the heat flux q2 is transmitted to the measuring element 2 and the heat flux Q _{g is} returned to the heat source 1 by the pipe 5.

The following mathematical relationships exist between the above heat flows:

Q _P = Qi + qi (i) Qg = Qz - q2 (2) Qo = Qi ~ Q2 (3) Qs ⁼ Q _P - Qg (4)

where

Q _p - heat flow from heat source;

Q _g - heat flow back to the heat source;

Q _o is the amount of heat consumed by the heat sink;

Q _s is the amount of heat used in the system "heat sink plus measuring element";

qi, q ₂ - heat quantities transmitted to the measuring element.

The design of the measuring element shall be such as to maintain the condition;

Qi / qi = Q2 / q2 = K, where

K - heat transfer coefficient.

Then:

Qi = K _qi (5)

Q? = Kq ₂ (6)

Adding the values (5) and (6) to equation (4) gives

Q _s = K qi + qi - (K q ₂ - q ₂ ) = (K -1) (qt - q ₂ ) (7)

If the measuring element is a heat-conductive rod of uniform cross-section throughout its length, the values qi and q ₂ may be expressed as follows:

qi = cm (t _p - t _a ) (8) q ₂ = cm (t _g - t _a ) (9) where c is the heat capacity of the measuring element, m is the mass of the measuring element, t _a is the ambient temperature of the measuring element, t _p is the temperature of the measuring element at point P, t _g is the temperature of the measuring element at point G.

Adding the values (8) and (9) to equation (7) gives

Q _s = (K -1) cm (t _p - t _g ) (10)

The difference in temperature between the supply and return of the heat transfer medium to the ends of the measuring cell shall not exceed 60 degrees C.

By selecting the appropriate material for the measuring element (aluminum, copper alloys, low-alloy steels), the change in the heat transfer coefficient K and the heat absorption C from the temperature of the selected material does not exceed 2%. The mass of the measuring element is a constant. Thus, it can be assumed that the product (K -1) c m is a constant value C with an error not exceeding 2%.

C = (K-1) cm (11)

This way

Q _s - C (t _p - t _g ) (12)

Size C can be calculated or determined experimentally.

The quantities t _p and t _g form the measuring part of the measuring element.

Claims (1)

DEFINITION OF INVENTION The differential heat measurement method uses a portion of the heat supplied to the sampler 5 and the measurement result is obtained using a known multiplication factor, characterized in that the heat flow carried by the feed and return heat carrier heats the measuring element quantity.