JPS58127156A - Measuring method for convection heat transmissibility and device thereof - Google Patents

Abstract

PURPOSE:To enable measuring of only a convection heat transmissibility, by a method wherein a flat plate is partitioned into two parts having different radiation rates, and a measurement is made on a quantity of radiation heat and an atmosphere temperature at a time when temperature is controlled so that surface temperatures at all parts are equal to each other. CONSTITUTION:A flat plate 11 is partitioned into two flat parts 11a and 11b, heat flow meters 12a and 12b are mounted to the backs thereof, heating plates 13a and 13b are further attached to the back thereof, and a temperature controller 15 is connected thereto. A temperature measuring elements 14a and 14b are located in the proximity of the surfaces of the flat plates 11a and 11b, and a temperatures element 17 is installed to the surface side thereof. In this constitution, based on the outputs of the temperature elements 14a and 14b, the surface temperature of the two flat plates 11a and 11b are made equal by the temperature controller 15. A measurement is conducted on the heat flow densities of the heat flow meters 12a and 12b under this condition to measure the atmosphere temperature of the temperature measuring element 17. Based on the measurements, only a convection heat transmissibility can be computed from a given computing formula.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a measuring method and a measuring device for measuring the convective heat transfer coefficient regarding a heat generating plane having a desired size when heat is radiated from the heat generating plane.

It is a well-known fact that the heat transfer phenomenon in which heat is radiated or absorbed from the surface of an object toward a gas can be explained as the sum of convection heat transfer and radiation heat transfer. However, it is difficult to separate these two heat transfer modes and determine the amount of heat transfer and also the heat transfer coefficient (convective heat transfer coefficient and radiant heat transfer coefficient) from the perspective of understanding the heat transfer situation or the thermal equipment. Although this is an important issue from the standpoint of thermal space design, due to the lack of appropriate measurement methods and equipment, it has only been possible to separate it by calculation using empirical values. In particular, it has been desired to develop a method and device for easily and accurately determining the above-mentioned two heat transfer amounts or heat transfer coefficients as design materials for maintaining more comfortable indoor living spaces. .

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a measuring method and apparatus capable of measuring only the convective heat transfer coefficient.

The present invention will be explained in detail below.

First, when carrying out the method of the present invention, a flat plate of a predetermined size is used, the surface of which is divided into at least two portions and processed so that the divided portions have different emissivities. When evaluating the convective heat transfer coefficient of a living space, it is necessary to replace it with a heating plate that has dimensions equivalent to the dimensions of a specific part of the human body, and since the value of the convective heat transfer coefficient varies depending on the dimensions, which Whether a flat plate with a certain size is required depends on the size and shape desired by the measurer. FIGS. 1(a) to 1) are diagrams showing examples of flat plates. The flat plate shown in this figure is a heat dissipating flat plate with a shape that is normally assumed, such as a rectangle, a square, and a circle.
: It is divided into two or more parts, and the divided parts are colored so that their emissivity is different from each other. The shape of the flat plate is not limited to that shown in the figure; any appropriate shape such as an ellipse or triangle may be used, and the method of coloring the strips does not necessarily have to be divided into equal parts, and the arrangement of the color strips is not limited to that shown in the figure. There is no need to stick to this example. Further, the method of setting the emissivity of the divided portions of the flat plate to an arbitrary value is not limited to band coloring.

Other methods include changing the emissivity by making the surface mirror-like or creating some irregularities through polishing, and further changing the emissivity by changing the thickness of the oxide film, such as the anodic oxide film on aluminum. Arbitrary emissivities can also be obtained using these methods.

Next, taking the flat plate shown in FIG. 1(a) as an example, the heat transfer situation when the flat plate is placed in a space will be analyzed. Assuming that the emissivity of each colored surface 1.2 is εI+ε2 (see Figure 2), for the colored surface l, Q+-αC1(Ts+-Ta)+ε1cr
(Tsr −Tw?)・・・・・・・・・・・・(1) For colored surface 2, q2=ac2(Tst−'J'a)+tt
a(Tst'−π−)・・・・・・・・・・・・(2
) (W/ m' or kcIl/lII''h) αC1; Colored surface 10 convective heat transfer coefficient (W/(ge・K) or d/bah''C) αC2; Colored surface 20 convective heat transfer coefficient ( W/(♂・K) or day/ga h'c) Tss; Colored surface 1■Surface temperature (K) Tsz; Colored surface 20 surface temperature (K) TA; Temperature of atmosphere (K) εyi; Band Color surface 10 surface emissivity C2; surface emissivity of color surface 2 σ Nystea-Amboltzmann constant Tw; average radiant temperature of opposing wall surface (K) (11, (in equation 21, surface temperature Ts of color surface 1 and 2
t and Ts2 as T s+ = T sz = T s , -0
”=I31, αC
1 yo αc2 d αC……(4) −4 becomes +11 under the condition of equation (3), and (Ts+ −Tw) from the +21 equation.

When the term (T sz' - Tw') is eliminated, the convective heat transfer coefficient αC becomes - ε2 qt - C1qt "' (61-εt) (Ts-TA) """"
It is found as “”. The condition in equation (3) above, that is, controlling the surface temperature of both colored surfaces equally, can be easily achieved using a commercially available temperature controller, and is correct considering that the convective heat transfer coefficient changes depending on the surface temperature. This is an important measurement condition from the viewpoint of determining the convective heat transfer coefficient. q
l * qt can be easily measured by installing a heat flow meter on the back side of the central part of colored surfaces 1 and 2. Furthermore, the emissivity ε of the colored surface! , ε2 are unlikely to cause discoloration O, and if one side is coated with black paint and the other side is coated with aluminum foil or aluminum paint so that the difference in emissivity is large, the emissivity is small and relatively low. There is also little change over time. These emissivity values can be easily determined using a commercially available emissivity meter. Furthermore, the temperature of the atmosphere can be measured by a temperature measuring element having a structure that shields thermal radiation.

Next, the structure of the device according to the present invention will be described.

FIG. 3 is a diagram showing the basic configuration of the device according to the present invention.

First, flat plates 11a and llb whose εl and ε2 are known are arranged in parallel to form a flat plate 11 having a predetermined size as a whole. Heat flow meters (mN for measuring heat flow density W/f) 12a and 12b are placed near the center of the back surface of each flat plate 11a and llb, respectively.
Further, on the back side of these heat flow meters 12a, 12b, a heating plate 18a, which is about the same size as the flat plates 11a, llb, is arranged.
13b is arranged. Further, temperature measuring elements 14a and 14b are arranged near the surfaces of the flat plates 11a and llb, respectively. on the other hand,
A temperature controller 15 is prepared, and the heat generation amount of the heating plates 18a, 18b is controlled based on the output of the temperature measuring elements 14a, 14b, so that the surface temperature of the flat plates 11a, llb is kept at a constant value (same temperature).
Make it so that (The heating plate, the temperature measuring element, and the temperature controller constitute a temperature control device 16 that maintains the surface temperature of the flat plates 11a and llb to a constant value.) Also, there is a A temperature measuring element 17 is installed. Note that since the surface properties of the flat plates 11a and llb affect the value of the convective heat transfer coefficient, they are usually finished with smooth surfaces.

In the apparatus having the above configuration, the surface temperature of the flat plates 11a and 11b can be kept at a constant value by the temperature control device 16, and the surface temperature of the flat plates 11a and 11b can be kept at a constant value by the heat flow meters 12a and 12b.
The heat flow density q+ Iq2 on the surface of can be measured,
The ambient temperature TA can be determined by the temperature measuring element 17, and the surface temperature Ts of the flat plate 110 can be determined by the temperature measuring element 14a or 14b. and flat plate 11a, ll
Since the emissivity and ε11ε2 of each surface of b are clear,
The convective heat transfer coefficient αC can be measured using the above-mentioned equation (5).

The above is an explanation of an apparatus in which the surface of a flat plate is divided into two parts, but the surface of the flat plate is divided into three or more parts and the convective heat transfer coefficient is calculated from each of two different surfaces. It is possible to check the accuracy of the measurement.

Next, the results of experiments conducted using a concrete fabrication of the current heat transfer coefficient measuring device according to the present invention will be described.

In this experiment, an apparatus was manufactured for the purpose of determining the convective heat transfer coefficient of a square flat plate with a total size of 300 m x 3001 nn. The manufactured device has the structure shown in Figures 1 to 7. 4 to 6 are diagrams showing the structure of the main body of the apparatus. The main body of the apparatus is made up of a flat plate 28 attached to the opening of a box 21 with a rubber gasket 22 interposed therebetween.

The box body 21 is a wooden box 2 divided into three by partition plates 24 and 24.
A frame 26 made of a heat insulating material is attached to the outer periphery of the frame 5. The external dimensions of this box body 21 are 320 cm (height)
x 320 (width) x 65 (thickness). flat plate 28
is made of three stainless steel plates (300tm x 10 (17aw)
X, 2m) 27 a N27 c are arranged so that the front side is flat. Stainless steel plates 27a-27
In the center of C there are holes (3 Otsuo XJ4 tll) 28a~
28c are formed in these holes 288 to 28C, respectively.
c is inserted. Stainless steel plates 27b, 29b
The surface of the stainless steel plate 27C is coated with black paint.
, 29C are coated with white paint. Further, the surfaces of the stainless steel plates 27a + 29a remain made of stainless steel. Each stainless steel plate 27a, 29a, 27b
, 29b, 27c, and 29c at a temperature of 30''C were actually measured, and found that 6M = 0. / εB = 0.I9 εW = QI3.

Further, FIG. 7 is a diagram showing the arrangement of measurement elements in the stainless steel plates 27b and 29b.

As shown in this figure, the stainless steel plate 29b has a temperature measuring element (
cc thermocouple) 80 and a resistance temperature detector 81 are provided. Also, a heat flow meter 82 is provided on the back side of this stainless steel plate 29b.
is installed. Also, on the rear side of the stainless steel plate 27b, a plastic plate 88 is provided surrounding the stainless steel plate 29b.
is installed. An aluminum plate 84 is attached to the rear side of the heat flow meter 82 and the plastic plate 88.

A planar heater 85 is attached to the rear surface of the aluminum plate 84. The arrangement of the measuring elements on the stainless steel plates 27b and 29b is as described above, and the measuring elements are arranged on the stainless steel plates 27a, 29a, 27c, and 29c in the same manner as above. Moreover, a temperature measuring element (cc thermocouple) 86 for measuring the ambient temperature is arranged particularly on the surface side of the stainless steel plates g7b and 29b. In the above configuration, the output of the heat flow meter 82 is
It is recorded in . In addition, the output of the resistance temperature detector 81 is input to the temperature controller 38, and the temperature controller 81
8 adjusts the amount of heat generated by the heater 850 based on the same output. Further, the output of the temperature measuring element 80.degree. 86 is input to a precision thermometer 89. Note that the sensitivity of the heat flow meter 82 used here is 0. /za@V/led/
7h).

The experimental method was to place the measuring device configured as described above in a closed space (approximately /m square) surrounded by a plywood board, and measure the convective heat transfer coefficient with the heat dissipation surface facing upward in a windless state. . The measurement results are shown in Table 1. The results shown in Table 1 show that the convective heat transfer coefficient due to W, H, Gi ed t
This substantially matches the value of 3.7 calculated from 9g(Ts-TA)0°25.

As is clear from the explanations in Table 1 and above, according to the present invention, the effect of easily measuring the convective heat transfer coefficient can be obtained.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are all plan views of the flat plate used to carry out the method of the present invention, and Figure 2 shows the heat transfer state when the flat plate shown in Figure 1 (a) is placed in a space. FIG. 3 is a diagram showing the basic configuration of the measuring device according to the present invention, FIG. FIG. 6 is an exploded perspective view of the main body of the apparatus, and FIG. 7 is a diagram showing the arrangement of measuring elements in the measuring apparatus. 11, 28--...Flat plate, 12a, 12b, 82
-'-'-・Heat flow meter, 16...Temperature control device,
17, 86... Temperature measuring element, 80... Temperature measuring element. Applicant Tokyo Electric Power Company Showa Denko Co., Ltd. Figure 1 (O) (b) (cl
Id) (e)
(f) Figure 2 Figure 3 Figure 4 Figure 5 Figure 7 Procedural amendment, a. 1. Indication of the case 1982 Patent Application No. 10490 2. Name of the invention Method for measuring convective heat transfer coefficient and Device 3. Person making the amendment: Patent applicant Tokyo Electric Power Company, Inc. (and 1 other person) 4. Agent

Claims (1)

[Claims] 1. Using a flat plate having a predetermined size whose surface is divided into at least two parts and processed so that the divided parts have different emissivities from each other, When the temperature is controlled so that the surface temperature of each part is equal, the amount of heat dissipated from each part and the temperature of the atmosphere in the part where the flat plate is present are measured, and based on the measurement results, the convection of the flat plate is A method for measuring convective heat transfer coefficient Q, characterized in that the heat transfer coefficient is measured. 2. A flat plate having a predetermined size whose surface is divided into at least two parts and processed so that the divided parts have different emissivities from each other, and a heat flow density that radiates heat from each of the above parts of this flat plate. , a temperature control device that equally controls the surface temperature of each part of the flat plate, and a temperature measuring element that measures the temperature of the atmosphere in the part where the flat plate is present. A device for measuring convective heat transfer coefficient.