CN201788161U - Soil thermal resistivity measuring probe based on point heat source method - Google Patents

Abstract

The utility model discloses a soil thermal resistivity measuring probe based on the point heat source method. The probe adopts a spherical structure and comprises a hollow metal spherical shell, insulating heat conducting filler, an electrical heating device and a temperature measuring thermocouple; a round hole and a strip-shaped groove gap are formed on the spherical shell; the electrical heating device is arranged at the internal center of the sphere; a temperature measuring probe of the thermocouple is mounted in the groove gap on the outer surface of the metal sphere; the spherical shell is filled up with the insulating heat conducting filler; the electrical heating device is sealed and positioned through the insulating heat conducting filler; and the temperature measuring probe of the thermocouple is separated from the metal spherical shell through insulating heat conducting silica gel. The probe is used conveniently, and the measurement result is accurate and reliable; the probe can be used not only for sample measurement in a laboratory but also for direct measurement of soil thermal resistivity on the spot under the condition that the soil structure is not damaged, and is particularly suitable for being used for measuring the thermal resistivity of soil within the depth range that various power cables, heating power pipes and other facilities are buried; and the soil thermal resistivity measuring probe based on the point heat source method has high measuring accuracy and wide range of application, and is flexible and convenient in operation.

Description

Soil thermal resistivity measuring sonde based on the heat point source method

Technical field

The utility model relates to a kind of soil thermal resistivity measuring sonde device based on the heat point source method, belongs to field of measuring technique.

Background technology

The thermal resistivity of soil is one of basic parameter of soil, determines that the method for soil thermal resistivity has two big classes, the one, and sampling method is promptly to measuring by instrument in the laboratory after the soil sample.But the experiment indoor sample can not accurately reflect the parameter of on-site soil, can introduce error; Another kind method is the thermal resistivity of in-site measurement soil, this method can keep real soil regime, have only at the scene and measure in real time, could satisfy various designs, construction and management process the soil moisture, real-time, the accurate Testing requirement of coefficient of heat conductivity.But present domestic ready-made measurement mechanism and the method for testing of also lacking.

Patent of invention (publication number: CN101320007A, title: pin is visited method material thermal conductivity measurement apparatus and material thermal conductivity measurement apparatus) and patent of invention (publication number: CN201222042Y, title: material thermal conductivity measurement apparatus) disclose a kind of pin and visited the method material thermal conductivity measurement apparatus based on the line heat source principle, it is the probe of 53mm that this method adopts diameter 0.7mm, length, inside is provided with the electrical heating wire of 0.0762mm, is applicable to the thermal conductivity measurement of liquid, gas and solid dielectric.But the measuring sonde in this method is the probe-type structure, and probe is made difficulty, and because the probe length restriction only is fit to small size sample is measured, can't be applied to the in-site measurement of big depth range soil thermal resistivity.

Utility model patent (publication number: CN2310994Y; title: a kind of probe that is used for measured soil temperature, humidity) but a kind of probe of measured soil humiture is disclosed; comprise the internal protective cover that has air hole and humidity-sensitive element, change-over circuit; this probe is long garden column structure; mainly act as the obstruction of the logical steam vent in the protective sleeve that can prevent earth effectively; structure is complicated, and on-the-spot detectability is poor.

Patent of invention (publication number: CN 101105467A, title: soil thermal resistivity determinator and method thereof) a kind of soil thermal resistivity determinator and method thereof are disclosed, can be used to test the soil thermal resistivity of geothermal heat pump air-conditioning system under soil heat extraction or two kinds of patterns of heat-obtaining, be primarily aimed at the underground degree of depth and measure, but this method does not relate to the shape and structure particular content of probe at the thermal resistivity of 40～100 meters soil.

Summary of the invention

The purpose of this utility model is to have proposed a kind of easy to use, the accurate and reliable soil thermal resistivity of measurement result measuring sonde, both can be used for the laboratory sampling and measuring, again can be under the condition of not destroying soil texture, on-the-spot directly measured soil thermal resistivity is particularly useful for the measurement of soil thermal resistivity in the facility depth of burying scopes such as various power cables, heat distribution pipeline.

The technical solution of the utility model is: based on the soil thermal resistivity measuring sonde of heat point source method, it is characterized in that: measuring sonde is a chondritic, metal spherical shell by a hollow, the insulating heat-conductive filling material, electric heater unit and temperature thermocouple are formed, have a circular hole on the spherical shell, a strip groove slit, electric heater unit is positioned at the ball center, the thermocouple temperature measurement probe is installed in the groove slit of Metal Ball outside surface, the electric heater unit power feeder is drawn outside the spherical shell by circular hole, the Thermocouple Temperature Signal transmission line is introduced in the spherical shell by circular hole, connect temperature probe in the strip groove slit again along the spherical shell inwall, metal spherical shell inside has the insulating heat-conductive filling material to enrich to fill up, electric heater unit and feeder line thereof, the Thermocouple Temperature Signal transmission line is by sealing of insulating heat-conductive filling material and location, and metal spherical shell and electric heater unit and feeder line thereof insulate.

Aforesaid soil thermal resistivity measuring sonde based on the heat point source method, it is characterized in that: electric heater unit links to each other with the direct supply of adjustable power, as the heating source of measurement point.

Aforesaid soil thermal resistivity measuring sonde based on the heat point source method is characterized in that: the heat conductive silica gel with insulation between thermocouple temperature measurement probe and metal spherical shell separates.

The beneficial effects of the utility model are: can come the measured soil coefficient of heat conductivity by sampling, also can be under the situation of not destroying soil texture, and the scene is directly measured the soil moisture and coefficient of heat conductivity, measuring accuracy height, applied range, flexible and convenient operation.

Principle of work of the present utility model: because the metal spherical shell is built-in with heating arrangement, at spherome surface the thermocouple temperature measurement probe is installed, provide firm power to make heating arrangement heating by power supply during measurement,, Metal Ball can be considered as heat point source when enough hour of Metal Ball diameter.

When measuring beginning, establish time t=0, heat point source in infinitely great uniform dielectric instantaneous send certain heat after, the temperature rise function at τ range points thermal source r place is at any one time:

$\mathrm{\θ}=\frac{Q_d}{\mathrm{c\ρ}\left(4\mathrm{\π\α\τ}\right)3/2}{e}^{-\frac{{\mathrm{\γ}}^2}{4\mathrm{\α\τ}}}---\left(1\right)$

In the formula:

Q _d: the instantaneous thermal value of heat point source, J;

C: the specific heat capacity of medium, J/kg. ℃;

ρ: density of medium, kg/m ³

α: the thermal diffusion coefficient of medium, m ²/ s;

τ: in thermal source metapyretic any time, s.

Following formula is carried out integration to time variable τ, promptly can obtain continuing separating of heat point source temperature field.

If continuing the calorific intensity of heat point source is q _d, t is after second, apart from the temperature rise θ at thermal source r place in the thermal source heating _tFor:

${\mathrm{\θ}}_t={\∫}_0^{\mathrm{\τ}}\mathrm{\θdt}=\frac{q_d}{4\mathrm{\π\λ\γ}}[1-\mathrm{erf}\left(\frac{r}{\sqrt{4\mathrm{\α\τ}}}\right)]---\left(2\right)$

In the formula:

λ: the pyroconductivity of medium;

Be error function, when

Enough little, promptly during Metal Ball diameter enough little or heat time heating time of long enough, Can ignore, show as the Metal Ball surface temperature and be tending towards a certain constant value θ.At this moment, can get by following formula:

$\mathrm{\λ}=\frac{q_d}{4\mathrm{\π\θ\γ}}$

Description of drawings

Accompanying drawing 1 is the soil thermal resistivity measuring sonde synoptic diagram of the utility model embodiment based on the heat point source method.

Embodiment

Below in conjunction with drawings and Examples the utility model is described further.

Description of reference numerals: 1-Thermocouple Temperature Signal transmission line, 2-electric heater unit power feeder, 3-circular hole, 4-hollow metal spherical shell, 5-thermocouple temperature measurement probe, 6-strip groove slit, 7-electric heater unit, 8-insulating heat-conductive filling material.

As shown in Figure 1, soil thermal resistivity measuring sonde based on the heat point source method, mainly comprise: hollow metal spherical shell 4, insulating heat-conductive filling material 8, electric heater unit 7, thermocouple temperature measurement probe 5 is formed, have a circular hole 3 on the spherical shell, a strip groove slit 6, electric heater unit 7 is positioned at the ball center, thermocouple temperature measurement probe 5 is installed in the groove slit 6 of Metal Ball outside surface, electric heater unit 7 power feeders 2 are drawn outside the spherical shell by circular hole 3, Thermocouple Temperature Signal transmission line 1 is introduced in the spherical shell 4 by circular hole 3, connect temperature probe 5 in the strip groove slit 6 again along the spherical shell inwall, there are insulating heat-conductive filling material 8 substantial filling up metal spherical shell 4 inside, electric heater unit 7 and feeder line 2 thereof, Thermocouple Temperature Signal transmission line 1 is by 8 sealings of insulating heat-conductive filling material and location, and metal spherical shell 4 insulate with electric heater unit 7 and feeder line 2 thereof.

In the in-site measurement, hollow metal spherical shell 4 is embedded in place to be measured, the direct supply of heating arrangement 7 with a power invariability is connected, logical temperature-detecting device reads by thermocouple temperature measurement probe 5 temperature values that measure, when temperature value is tending towards constant, can calculate the pyroconductivity and the thermal resistivity of soil to be measured, hollow metal spherical shell 4 can be embedded in the different degree of depth according to demand, is convenient to measure the soil thermal resistivity of diverse location.

Claims (3)

1. based on the soil thermal resistivity measuring sonde of heat point source method, it is characterized in that: measuring sonde is a chondritic, metal spherical shell by a hollow, the insulating heat-conductive filling material, electric heater unit and temperature thermocouple are formed, have a circular hole on the spherical shell, a strip groove slit, electric heater unit is positioned at the ball center, the thermocouple temperature measurement probe is installed in the groove slit of Metal Ball outside surface, the electric heater unit power feeder is drawn outside the spherical shell by circular hole, the Thermocouple Temperature Signal transmission line is introduced in the spherical shell by circular hole, connect temperature probe in the strip groove slit again along the spherical shell inwall, metal spherical shell inside has the insulating heat-conductive filling material to enrich to fill up, electric heater unit and feeder line thereof, the Thermocouple Temperature Signal transmission line is by sealing of insulating heat-conductive filling material and location, and metal spherical shell and electric heater unit and feeder line thereof insulate.

2. the soil thermal resistivity measuring sonde based on the heat point source method as claimed in claim 1, it is characterized in that: electric heater unit links to each other with the direct supply of adjustable power, as the heating source of measurement point.

3. the soil thermal resistivity measuring sonde based on the heat point source method as claimed in claim 1 is characterized in that: the heat conductive silica gel with insulation between thermocouple temperature measurement probe and metal spherical shell separates.

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