CN103983365B - Multi-measuring-head transient radiation heat flow meter and measuring method for thermal radiation heat flow density - Google Patents

Abstract

The invention discloses a heat flow meter for rapid response non-contact measurement of heat flux density, which includes a multi-sensitive surface measuring head, a heat sink body, a heat sink body temperature measuring thermocouple, a data acquisition device, a data processing and display device, and according to different absorption Two identical materials with the same intensity, when subjected to the same intensity of radiant heat flow, have different temperatures, establish the relationship between the radiant heat flux density and the temperature difference between the two sensitive surfaces, and at the same time avoid system errors, and develop a method that can satisfy the space It can be used in a technical vacuum environment, and can also be used in a convective environment on the ground. It has a simpler structure and can work continuously. It can be connected in series to form a thermopile to increase the temperature difference thermoelectric potential and reduce the error in the measurement. It is a high-precision transient radiation heat flow meter. .

Description

Multi-probe transient radiant heat flow meter and method for measuring heat radiant heat flux

technical field

The invention relates to a multi-probe transient radiation heat flow meter for measuring various heat radiation heat flux densities of steam boilers, soaking furnaces, heat transfer pipes, and space heat radiation, and the measurement of heat radiation heat flux density using the heat flow meter method.

Background technique

Radiation heat flow meters have important applications in many fields such as solar energy, space technology, meteorology, industry, metallurgy, energy, power, air conditioning, etc. The theory and technology of heat flow detection have attracted more and more attention. The currently used full radiation heat flow meters are divided into heat conduction steady-state heat flow meters and lumped heat capacity heat flow meters, both of which are designed based on the principle of heat balance. In order to improve the measurement accuracy of fluctuating radiant flow, research on high-precision transient radiant heat flowmeter is needed.

The main types of common transient radiant heat flow meters are composed of a single sensitive surface. The first one is to obtain the radiant heat flow by establishing the relationship between the temperature change of the sensitive surface and the radiant heat flow, but the temperature change of the sensitive surface is not directly measured by the sensitive surface itself, but it must be carried out by using other thermocouples, so that the thermocouple There is a heat conduction process between the copper sheet and the copper sheet. In order to compensate the dynamic error between the temperature measured by the thermocouple and the real temperature of the copper sheet due to time delay when the radiation heat flow changes suddenly, the data processing usually needs to be compensated, which will affect Measured errors and response times. The second type, the round foil transient heat flow meter, transfers heat through the contact between a single constantan sensitive surface and the copper heat sink, and establishes the relationship between the heat flow and the temperature gradient of the sensitive surface, but the contact area is large, and the temperature rise of the heat sink will affect To the measurement results, it is not conducive to working for a long time. The third type, the adiabatic transient heat flow meter, is designed to track the temperature change of the sensitive surface, so that the sensitive surface and the tracking surface maintain the same temperature, and establish the relationship between the radiation heat flow and the tracking heating amount. This method is beneficial to long-term measurement. However, the structure is more complex, and there are many factors affected by interference.

Contents of the invention

In view of the above problems, the present invention is designed based on the principle of heat balance, combined with all the advantages of the circular foil heat flow meter and the adiabatic transient heat flow meter, the model of the transient radiation heat flow meter is cleverly designed, and the temperature is directly measured by the differential thermocouple of the double measuring head. Establish the relationship between the radiation heat flux density and the temperature difference between the two sensitive surfaces, and avoid systematic errors at the same time, develop a high-precision transient radiation that can be used in the vacuum environment of space technology and can also be used in the ground convection environment heat flow meter.

Technical scheme of the present invention is:

A radiant heat flow meter with multiple sensitive surface measuring heads, comprising a first heat sensitive surface measuring head, a second heat sensitive surface measuring head, a heat sink body, a heat sink body temperature measuring thermocouple, a data acquisition instrument, a control system, and data processing and display device section,

The first heat-sensitive surface measuring head is provided with a first heat insulating material, and the second heat-sensitive surface measuring head is provided with a second heat-insulating material. The first heat-sensitive surface measuring head and the second heat-sensitive surface measuring head The heat absorption rate of the head is different, the first heat-sensitive surface measuring head and the second heat-sensitive surface measuring head are insulated from each other, and the radiant heat flux received by each other from the heat source is the same under the same conditions.

The heat sink body is connected with the temperature measuring thermocouple of the heat sink body, the first heat-sensitive surface probe and the second heat-sensitive surface probe are respectively connected with the heat sink body, the first heat-sensitive surface probe, the second heat-sensitive surface probe The second heat-sensitive surface probe and the heat-sink body thermocouple are respectively connected to the data acquisition instrument, and the thermal signals received by the first heat-sensitive surface probe, the second heat-sensitive surface probe, and the heat-sink body thermocouple are transmitted to the data In the acquisition instrument, the analog signal generated by the data acquisition instrument is amplified and A/D converted into a digital signal and sent to the control system. The data acquisition instrument is controlled by the control system, and the temperature signal is transmitted to the data processing and display device.

Preferably, the first heat-sensitive surface measuring head and the second heat-sensitive surface measuring head are two thin constantan sheets with the same material size and different surface roughening and coloring treatments.

Preferably, among the thin constantan sheets with different surface roughening processes and coloring treatments, one of them is treated with a rough surface coated with dark paint, and the other is treated with a smooth surface coated with light colored paint.

Preferably, the control system is a computer with a control program,

Preferably, no quartz glass cover is added outside the heat-sensitive surface measuring head of the radiant heat flow meter,

Preferably, the heat sink is connected to the heat-sensitive surface probe through copper wires.

The beneficial technical effect that the present invention obtains with respect to prior art is:

1. The multi-probe transient radiant heat flow meter of the present invention, two heat-sensitive surfaces and heat sinks constitute multiple sets of copper-constantan thermocouples, which can instantly measure the temperature between the sensitive surfaces and obtain the radiation heat flux;

2. Part of the error of the system is eliminated, and the measurement result is closer to the real value;

3. The multi-probe transient radiant heat flowmeter of the present invention can be measured in vacuum, or in the atmosphere or under complex conditions; The sensitive measuring head is equipped with a quartz glass cover, because the glass cover will absorb part of the radiation energy, which increases the error of the experiment. Due to the same environment, the dual-probe design can eliminate the influence of environmental convective heat transfer on the measurement by subtraction during calculation. Therefore, the quartz glass cover can be omitted in the atmospheric environment, so as to eliminate the absorption of heat radiation of a certain band by the quartz glass itself.

4. In the multi-probe transient radiant heat flow meter of the present invention, the sinking body and the measuring head of the heat-sensitive surface are connected by copper wires, so that the distance between the heat sinking body and the sensitive surface is relatively far, the temperature is not easy to rise rapidly, and it can work stably for a long time.

detailed description

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is the sensing device structural diagram of multi-probe transient radiant heat flow meter of the present invention;

In the figure: 1 is the measuring head of dark rough thin constantan sheet; 2 is the measuring head of light-colored smooth thin constantan sheet; 3 is the copper heat sink body; a, b, and c are connecting copper wires.

The multi-probe transient radiant heat flow meter of the present invention includes two thin constantan sheets with the same size and material, the mass is m, and the area is A, and the dark rough thin constantan sheet 1 is coated with dark paint for rough surface treatment , the temperature is T ₁ , the light-colored and smooth thin constantan sheet 2 is coated with light-colored paint for smooth surface treatment, and the temperature is T ₂ , the two thin constantan sheets are respectively used as the heat-sensitive surface measuring heads of the heat flow meter, and the back of the thin constantan sheet is With heat insulating material, there is no heat exchange between the two thin constantan sheets. The radiant heat flux received by them from the heat source is the same under the same conditions. Let a ₁ and a ₂ represent the absorption rate of dark rough thin constantan sheet 1 and light smooth thin constantan sheet 2 respectively.

As shown in Figure 1, three thermocouples are composed of a dark rough thin constantan sheet 1, a light-colored smooth thin constantan sheet 2 and a copper heat sink body 3. The temperature of the copper heat sink body is T ₀ . Measured by the thermocouple, the temperature T ₁ of the dark rough thin constantan sheet 1 is obtained by the two-point voltage ab, the temperature T ₂ of the light-colored smooth thin constantan sheet 2 is obtained by the two-point voltage bc, and the dark rough thin constantan The temperature difference T ₁ -T ₂ between the sheet 1 and the light-colored smooth thin constantan sheet 2 is obtained by ac two-point voltage, so that when the heat flow on the heat-sensitive surface changes, the temperature of the two heat-sensitive surfaces will be directly measured Variety.

The sensitive surface is idealized as a gray body, and the spectral absorptivity has nothing to do with the input radiation. After the heat-sensitive surface is subjected to the thermal radiation with a radiant heat flux density q from the heat source, the energy balance equations of the two thin constantan probes are respectively:

In the above formula, a ₁ is the absorptivity of the dark rough thin constantan sheet 1, a ₂ is the absorptivity of the light-colored smooth thin constantan sheet 2, q is the radiation heat flux density, A is the area of the thin constantan sheet, and m is The mass of the thin constantan sheet, c is the specific heat capacity of the thin constantan sheet, q _L1 is the heat exchange loss of the dark rough thin constantan sheet 1, and q _L2 is the heat exchange loss of the light-color smooth thin constantan sheet 2.

q _L1 and q _L2 include three parts of heat exchange loss. Respectively, the radiation loss from the measuring head on the heat-sensitive surface, the convective heat exchange loss between the thin constantan sheet and the air with the ambient temperature T _∞ , and the conduction heat exchange loss between the thin constantan sheet and the bottom surface of the back insulation layer with the temperature T _b , the The heat loss calculation method of the three parts is as follows:

1) When the radiation background temperature is very low, the radiation loss q _L11 and q _L12 of the dark rough thin constantan sheet 1 and the light smooth thin constantan sheet 2 are respectively:

q _L11 ＝ε ₁ σAT ₁ ⁴

q _L11 =ε ₂ σAT ₂ ⁴

In the formula, σ is the Stefan-Boltzmann constant, σ=5.670×10 ^-8 W/(m ² ·K ⁴ ), ε ₁ and ε ₂ are the dark rough thin constantan sheet 1 and the light smooth thin Constantan 2 emissivity. The absorption of energy by an object and the emission of electromagnetic waves by radiating heat to the outside are two processes in opposite directions. The heat absorbed by an object is the radiation energy falling on the object, which affects and changes the excitation of electrons, so that a part of the radiation energy is converted into heat energy and is absorbed. absorbed by the object. Objects emit heat by emitting electromagnetic radiation. Due to the excitation of electrons, heat energy is converted into radiation energy and emitted. When the object is regarded as a gray body, according to Kirchhoff's law, the radiation and absorption capacity of the object can be obtained from the study of the radiation heat transfer between the two surfaces:

That is to say, the emissivity and absorptivity of any object that can be regarded as a gray body are equal in value, which shows that the stronger the absorption ability of any object, the stronger its radiation ability, that is, those who are good at absorbing must be good at radiation. The above-mentioned relationship also exists for the blackness and absorptivity at a certain wavelength.

2) The convective heat transfer q _L21 and q _L22 of the dark rough thin constantan sheet 1 and the light-color smooth thin constantan sheet 2 with the air at the ambient temperature T _∞ are respectively:

q _L21 ＝hA(T ₁ -T _∞ )

q _L22 ＝hA(T ₂ -T _∞ )

In the above formula, h is the convective heat transfer coefficient, which is calibrated in advance, the positions of the two probes are relatively close, and the air above is connected. Here, T _∞ is considered to be consistent.

The approximate magnitude of the convective heat transfer coefficient h is:

Air natural convection 5~25;

Gas forced convection 20~100;

Natural convection of water 200~1000;

Forced convection of water 1000~15000;

Forced convection of oil 50~1500;

Condensation of water vapor 5000~15000;

Condensation of organic vapor 500~2000;

The boiling of water is 2500~25000.

3) The conduction heat transfer q _L31 and q _L32 of the dark rough thin constantan sheet 1 and the light-color smooth thin constantan sheet 2 through the back heat insulation layer to the bottom surface with temperature T _b are respectively:

q _L31 =λA(T ₁ -T _b )

q _L32 =λA(T ₂ -T _b )

In the above formula, λ is the thermal conductivity of the heat insulation layer. Since the properties and conditions of the back material are the same, it is obvious that Tb is the same here. Therefore, the total heat loss of the dark and light constantan sheets is:

q _L1 ＝ε ₁ σAT ₁ ⁴ +hA(T ₁ -T _∞ )+λA(T ₁ -T _b ) (3)

q _L2 ＝ε ₂ σAT ₂ ⁴ +hA(T ₂ -T _∞ )+λA(T ₂ -T _b ) (4)

Substitute equations (3) and (4) into equations (1) and (2) and subtract them to obtain the measurement equation of transient radiant heat flux in the atmosphere:

If there is no convective heat transfer loss in vacuum conditions, λ is the thermal conductivity coefficient of the heat insulation layer is small, when the temperature difference between the two sensitive surfaces is not particularly large, the temperature difference caused by the heat transfer of the back material is very small, and the transient radiation heat flux density formula of the space can be This further simplifies to:

The thermal signals received by the double-probe dark rough thin constantan sheet 1 and light-color smooth thin constantan sheet 2 are transmitted to the data acquisition instrument, and the analog signal is converted into a digital signal by amplification and A/D conversion and sent to the computer. The data acquisition instrument is controlled by computer software programming, and the temperature signal is transmitted to the corresponding data processing and display device part.

Claims (7)

1. a kind of radiation heatflowmeter of many sensitive areas gauge head is it is characterised in that include the first thermo-responsive face gauge head, second thermo-responsive Face gauge head, heat sink body, heat sink body temperature thermocouple, data collecting instrument, control system, with data processing and display device part；

It is provided with the first adiabator after the first described thermo-responsive face gauge head, after the second described thermo-responsive face gauge head, be provided with second Adiabator, the thermal absorptivity of the first thermo-responsive face gauge head and the second thermo-responsive face gauge head is different, the first thermo-responsive face gauge head and Mutually adiabatic between second thermo-responsive face gauge head, the radiant heat flux density received by from thermal source is identical under the same conditions 's；

Described heat sink body is connected with heat sink body temperature thermocouple, and described first thermo-responsive face gauge head, the second thermo-responsive face are surveyed Head be connected with heat sink body respectively, the first thermo-responsive face gauge head, the second thermo-responsive face gauge head, heat sink body temperature thermocouple respectively with number Connect according to Acquisition Instrument, and by the first thermo-responsive face gauge head, the second thermo-responsive face gauge head, the heat that heat sink body temperature thermocouple receives Signal is sent in data collecting instrument, and the signal that data collecting instrument produces is amplified, A/D conversion process is converted into digital signal and send Enter control system, by control system control data Acquisition Instrument, temperature signal incoming data is processed and display device part.

2. as claimed in claim 1 a kind of radiation heatflowmeter of many sensitive areas gauge head it is characterised in that the first thermo-responsive face is surveyed Head and the second thermo-responsive face gauge head be two panels size material consistent and through different rough surface PROCESS FOR TREATMENT and colouring process Thin constantan piece.

3. as claimed in claim 2 a kind of radiation heatflowmeter of many sensitive areas gauge head it is characterised in that described through different Rough surface PROCESS FOR TREATMENT and the thin constantan piece that processes of colouring, one of them is to apply at dark paint rough surface through surface Reason, another is to apply light color paint smooth finish surface through surface to process.

4. as claimed in claim 1 a kind of radiation heatflowmeter of many sensitive areas gauge head it is characterised in that described control system It is the computer with control program.

5. as claimed in claim 1 a kind of radiation heatflowmeter of many sensitive areas gauge head it is characterised in that described radiant heat flux It is not added with quartz glass cover outside the thermo-responsive face gauge head of meter.

6. as claimed in claim 1 a kind of radiation heatflowmeter of many sensitive areas gauge head it is characterised in that described heat sink body with Thermo-responsive face gauge head is connected by copper conductor.

7. to carry out heat radiation hot-fluid close for a kind of radiation heatflowmeter of the many sensitive areas gauge head described in any one using claim 1-6 The assay method of degree is it is characterised in that respectively obtain temperature T of the first thermo-responsive face gauge head₁, the temperature of the second thermo-responsive face gauge head Degree T₂, temperature T of heat sink body₀, temperature difference T between the first thermo-responsive face gauge head and the second thermo-responsive face gauge head₁-T₂, thermo-responsive When the hot-fluid that face is subject to changes, by the temperature change of direct measurement to two thermo-responsive faces；

Sensitive area is idealized as grey body, after thermo-responsive face is subject to the radiant heat flux density of self-heat power to be the heat radiation of q, two The energy-balance equation of thermo-responsive face gauge head is respectively：

$a_{1}qA=mc\frac{{\mathrm{dT}}_1}{dt}+q_{L1}---\left(1\right)$

$a_{2}qA=mc\frac{{\mathrm{dT}}_2}{dt}+q_{L2}---\left(2\right)$

In above formula, a₁For the absorbance of the first thermo-responsive face gauge head, a₂For the absorbance of the second thermo-responsive face gauge head, q is radiant heat Current density, A is thermo-responsive face gauge head area, and m is thermo-responsive face gauge head quality, and c is thermo-responsive face gauge head specific heat capacity,

q_L1And q_L2Heat exchange loss including three parts；Be respectively thermo-responsive face gauge head send radiation loss, thermo-responsive face gauge head with Environment temperature is T_∞Cross-ventilation heat exchange loss, thermo-responsive face gauge head and temperature are T_bThe conduction of back side thermal insulation layer bottom surface change Heat loss, the heat loss computational methods of this three part are as follows：

1) in the case of radiation background temperature is very low, the first thermo-responsive face gauge head and the second thermo-responsive face gauge head send radiation loss q_L11And q_L12It is respectively：

q_L11=ε₁σAT₁ ⁴

q_L12=ε₂σAT₂ ⁴

In formula, σ is Stefan Boltzmann constant, σ=5.670 × 10^-8W/(m²·K⁴), object is considered as grey body, ε₁、ε₂Respectively For the first thermo-responsive face gauge head and the second thermo-responsive face gauge head emissivity；

2) the first thermo-responsive face gauge head and the second thermo-responsive face gauge head are T with environment temperature_∞Air heat convection q_L21With q_L22It is respectively：

q_L21=hA (T₁-T_∞)

q_L22=hA (T₂-T_∞)

In above formula, h is convection transfer rate, is demarcated in advance, and relatively, upper air is connection to two probe location , T_∞It is consistent；

3) the first thermo-responsive face gauge head and the second thermo-responsive face gauge head are T by back side thermal insulation layer to temperature_bThe conduction of bottom surface change Hot q_L31And q_L32It is respectively：

q_L31=λ A (T₁-T_b)

q_L32=λ A (T₂-T_b)

In above formula, λ is thermal insulation layer heat conductivity, because backing material property condition is identical, T_bIt is consistent；

Obtain the first thermo-responsive face gauge head and the Total heat loss of the second thermo-responsive face gauge head is respectively：

q_L1=ε₁σAT₁ ⁴+hA(T₁-T_∞)+λA(T₁-T_b) (3)

q_L2=ε₂σAT₂ ⁴+hA(T₂-T_∞)+λA(T₂-T_b) (4)

By (3), (4) formula substitutes into (1) respectively, (2) subtract each other cancellation T_∞And T_bObtain transient radiation Heat flux calculation in an atmosphere Formula is：

$(a_1-a_2)q=\frac{mc}{A}\frac{d(T_1-T_2)}{dt}+\mathrm{\σ}({\mathrm{\ϵ}}_1{T_1}^4-{\mathrm{\ϵ}}_2{T_2}^4)+h(T_1-T_2)+\mathrm{\λ}(T_1-T_2)---\left(5\right)$

In vacuum condition, heat convection is not had to lose, λ is that thermal insulation layer heat conductivity is less, when two sensitive area temperature difference are not Especially big situation, backing material heat transfer causes temperature difference very little, and the transient radiation heat flow density formula in space can be further simplified as：

$(a_1-a_2)q=\frac{mc}{A}\frac{d(T_1-T_2)}{dt}+\mathrm{\σ}({\mathrm{\ϵ}}_1{T_1}^4-{\mathrm{\ϵ}}_2{T_2}^4)---\left(6\right)$

The thermal signal of the first thermo-responsive face gauge head and the second thermo-responsive face gauge head reception passes in data collecting instrument, analogue signal warp Amplify, A/D is converted into digital signal and sends into computer, by computer software programming control data Acquisition Instrument, by temperature signal Incoming and carry out corresponding data processing and display device part.