CN112326727A - Method for measuring soil heat recovery capability through thermal response test method - Google Patents
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
Abstract
The invention provides a method for measuring soil heat recovery capacity by a thermal response test method, which comprises the following steps: obtaining power data of a single well; starting a thermal response instrument for testing, simulating actual power and other powers to operate for a period of time in the single-port well, and immediately measuring the temperature of each stratum by using an interference-free ground temperature device after the heating operation is finished; placing for a period of time and measuring the temperature of each stratum in real time; and processing the data to obtain the soil recovery capability under different test conditions. The invention utilizes the thermal response testing technology and the non-interference ground temperature monitoring technology, considers that the underground temperature is higher than the temperature of the surrounding soil all the year round when in actual operation, and the underground heat radiates to the surrounding soil all the year round, measures the soil heat change condition under the working conditions of constant power and unit time, provides a mathematical algorithm to analyze the heat recovery capability of the constant heating of the soil in unit time, and can guide the design of an air conditioning system from the aspect of underground heat conduction.
Description
Technical Field
The invention belongs to the technical field of geothermal utilization, and particularly relates to a method for measuring soil heat recovery capacity through a thermal response test method.
Background
The ground source heat pump is one of the main technologies for shallow geothermal exploitation and utilization, low-grade shallow geothermal energy can be used for building heating after being collected and promoted by a heat pump technology, and the working principle of the ground source heat pump system is as follows: in winter, collecting heat in underground soil as a heat source for heating, and transferring the heat with lower temperature to an indoor user with higher temperature through a heat pump; in summer, the indoor heat, which is extracted at a higher temperature, is transferred to the subsurface soil, which is at a lower temperature.
The ground source heat pump system mainly comprises a geothermal energy acquisition system, a heat pump unit and an in-building system, the development and utilization of the geothermal energy of shallow rock-soil mass adopt a buried pipe ground source heat pump system, a circulating water pump provides power for a heat exchange medium in the system, the motor power of the circulating water pump controls the rotating speed of the circulating water pump, the rotating speed of the circulating water pump controls the flow rate of the heat exchange medium in the system, and the flow rate influences the heat exchange quantity, so when the circulating water pump is selected, the power of the pump and the flow rate in the system are comprehensively considered, and according to the relevant regulation of ground source heat pump system engineering technical specification (GB50366-2009), when the application area of the buried pipe ground source heat pump system is 3000-5000 square meters, a geotechnical heat response test is preferably carried out; when the building area is greater than or equal to 5000 square meters, a rock-soil thermal response test is carried out. Before the thermal response test of rock and soil, the field survey is carried out on the test site, the number of the test holes and the test scheme are determined according to the complexity of geological conditions, when the application area of the buried pipe ground source heat pump system is more than 10000 square meters, the number of the test holes is not less than 2, and for the test of 2 or more test holes, the measurement result is the arithmetic mean value.
For the geothermal energy industry, soil heat accumulation is a remarkable problem in the actual working condition work of a buried pipe, in most areas of China, the heat discharged to the underground in summer is larger than the heat absorbed in winter due to the fact that the cold load is larger than the heat load, the unit can form heat accumulation underground after long-time operation, the temperature of an underground constant temperature zone is gradually increased, the cold supply efficiency of a ground source heat pump is gradually deteriorated year by year, the normal use of the unit is affected, and in the design process of the ground source heat pump, the balance between the heat dissipation amount of the system to the underground in summer and the heat extracted from the soil in winter needs to be guaranteed.
Disclosure of Invention
Aiming at the explanation of the background technology, the invention provides a method for measuring the soil heat recovery capacity by a thermal response test method, which utilizes the thermal response test technology to compare and analyze the heat exchange capacity of the buried pipe and guides the design of an air conditioning system in the aspect of flow velocity economy of the buried pipe.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for measuring the heat recovery capability of soil by a thermal response test method comprises the following steps:
the method comprises the following steps of firstly, obtaining the heat load of a building according to the design data of the building, and obtaining the power data of a single well according to a thermal response heating power calculation formula, wherein the thermal response heating power is the product of the heat exchange quantity per linear meter and the depth of the single well;
step two, according to the time set by the requirement, the calculated constant power and other achievable powers start a thermal response instrument to test, the actual power and other powers are simulated, the thermal response instrument operates for a period of time in a single-hole well, the total soil temperature displayed by the thermal response instrument is read after the heating operation is finished, and the temperature of each stratum is immediately measured by an interference-free ground temperature device;
step three, placing for a period of time and measuring the temperature of each stratum in real time;
and step four, obtaining related test data, processing the data to obtain the soil restoration capacity under different test conditions, namely the non-interference soil temperature measurement soil restoration capacity.
In the above technical solution, the length of the shelf life in the third step can be selected according to the requirement, and the longest shelf life is the temperature recovery time of each stratum.
In the technical scheme, the interference-free ground temperature device adopts a structure that a temperature sensor is connected with a temperature measuring lead: namely, a 300m temperature measuring lead is used, the bottom of the temperature measuring lead is connected with a PT100 temperature sensor and a counterweight, and a group of interference-free ground temperature devices are arranged upwards at certain intervals.
In the technical scheme, the soil restoration ability is measured without interference in the fourth step, namely, the soil with multiple groups of gradient depths is measured from different T2Temperature recovery to a different T1Multiple sets of average rates of heat dissipated outwardly by temperature, T2The instantaneous total ground temperature is the instantaneous total ground temperature after the ground temperature is heated to a certain depth instantaneously after the heating; t is1Is heated and then placed for a period of time T and T1The total ground temperature at the same depth can be verified by the average rate of the heat emitted measured by the thermal response tester, and is obtained by the following formula:
from T for a certain depth/total soil2Temperature returns to T1Temperature difference of temperature:
ΔT＝(T2-T1)
wherein, T2-instantaneous certain depth/global ground temperature after heating; t is1After heating, standing for a period of time T and T1Same depth/overall ground temperature;
from T for a certain depth/total soil2Temperature returns to T1Average recovery rate of temperature:
wherein, t is the standing time of the soil, namely the temperature recovery time;
above depth/total soil from T2Temperature returns to T1Heat dissipated outward by temperature:
c, the specific heat capacity of the soil is the same as the depth of the temperature measuring point and is approximate to the average value of the whole well; l-flow of circulating water in the underground pipe; ρ — density of water;
thus, the depth/total soil is from T2Temperature returns to T1Average rate of heat dissipated outward by temperature:
the invention utilizes the thermal response testing technology and the non-interference ground temperature monitoring technology, considers that the underground temperature is higher than the temperature of the surrounding soil all the year round when in actual operation, and the underground heat radiates to the surrounding soil all the year round, measures the soil heat change condition under the working conditions of constant power and unit time, provides a mathematical algorithm to analyze the heat recovery capability of the constant heating of the soil in unit time, and can guide the design of an air conditioning system from the aspect of underground heat conduction.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The principle of the invention is as follows: the apparatus (instrument) used in the present invention is: the thermal response tester and the non-interference temperature measuring device are used for testing according to required power, the thermal response tester stops running after running for a period of time, the total formation temperature is read, then the thermal response tester waits for a period of time, a circulating pump of the thermal response tester is started again to reduce the temperature difference between heat exchange media in the pipe to be small enough, the total formation temperature is read, and finally the total soil recovery capability measured by the thermal response tester under the condition is calculated by using data obtained in the process. The non-interference temperature measuring device is normally opened in the process, test data are recorded in real time, the data are used for calculating to obtain the real-time accurate soil restoration capacity of each stratum, and the total soil restoration capacity can be verified. The specific implementation method comprises the following steps:
a method for measuring the heat recovery capability of soil by a thermal response test method comprises the following steps:
step one, obtaining the heat load of the building according to the design data of the building, and obtaining the power data of a single well according to a thermal response heating power calculation formula, wherein the thermal response heating power is the product of the heat exchange quantity per linear meter and the depth of the single well: in the embodiment, the depth of a single well is 200 meters, the heat exchange amount per linear meter is 28.5W, and the thermal response heating power is as follows: 28.5W/m 200m 5700W;
step two, starting a thermal response instrument for testing according to the calculated constant power 5700W and other achievable powers, simulating actual power and other powers, operating for 49 hours and 26 minutes in a single-ported well, and according to GB 50366-: 1. the rock-soil thermal response test is continuous and uninterrupted, and the duration time is not less than 48 h; 2. during the test period, the heating rate should be kept constant; 3. after the outlet temperature of the ground heat exchanger is stable, the temperature is preferably higher than the initial average temperature of rock soil by more than 5 ℃ and the maintaining time is not less than 12 h. After the heating operation is finished, reading the total soil temperature displayed by the thermal response tester, and immediately measuring the temperature of each stratum by using an interference-free ground temperature device;
and step three, after actual standing for 4 hours and 42 minutes, recovering the temperature to the initial average temperature of the rock soil, namely the temperature recovery time, maximally taking the time for recovering the heated temperature to the initial average temperature of the rock soil, calculating the recovery capability most accurately according to the maximum value, measuring the temperatures of all the stratums in real time, wherein the length of the standing time can be selected according to needs, and the longest standing time is the time for recovering the original value of the temperature of each stratum. And the total soil temperature was measured using a thermal response tester after the end of the shelf time.
Step four, obtaining relevant test data, processing the data to obtain the soil restoration capacity under different test conditions, namely the non-interference soil temperature measurement restoration capacity, the non-interference soil temperature measurement restoration capacity and the multi-group gradient depth soil from different T2Temperature recovery to a different T1Multiple sets of average rates of heat dissipated outwardly by temperature, T2The instantaneous total ground temperature is the instantaneous total ground temperature after the ground temperature is heated to a certain depth instantaneously after the heating; t is1Is heated and then placed for a period of time T and T1The total ground temperature at the same depth can be verified by the average rate of the heat emitted measured by the thermal response tester, and is obtained by the following formula:
total soil from T2Temperature returns to T1Temperature difference of temperature:
ΔT＝(T2-T1)＝20.4℃-14.1℃＝6.3℃
wherein, T2-instantaneous total ground temperature after heating; t is1The total earth temperature after the heating and the placement for a period of time t (the average rate of the heat emitted measured by the thermal response tester can be verified by measuring the temperature difference of each stratum through an interference-free earth temperature measuring device and weighting and averaging);
total soil from T2Temperature returns to T1Average recovery rate of temperature:
wherein, t is the standing time of the soil, namely the temperature recovery time;
total soil from T2Temperature returns to T1Heat dissipated outward by temperature:
c, the specific heat capacity of the soil is the same as the depth of the temperature measuring point and is approximate to the average value of the whole well; l-flow of circulating water in the underground pipe; ρ — density of water;
thus, the total soil is from T2Temperature returns to T1Average rate of heat dissipated outward by temperature:
in most areas of China, the summer cold load of a building is usually larger than the winter heat load, so that the heat release from a ground source heat pump system to soil in summer is larger than the heat taken from the soil in winter, heat taking in winter and summer is unbalanced, and the heat accumulation phenomenon in a pipe burying area is easily caused; through the method provided by the patent, the soil recovery capacity can be determined, the difference value of the heat release in winter and summer is divided by the recovery rate of the soil, and accordingly, the time required by the recovery of the necessary heat exchange capacity of the redundant heat of the soil in the non-energy supply season is calculated.
The interference-free ground temperature device used by the invention adopts a structure that a temperature sensor is connected with a temperature measuring lead: namely, a 300m temperature measuring lead is used, the bottom of the temperature measuring lead is connected with a PT100 temperature sensor and a counterweight, and a group of interference-free ground temperature devices are arranged upwards at certain intervals.
The thermal response tester used by the invention is equipment in the prior art, and mainly comprises a heater, a circulating pump, a display screen and the like.
When the temperature measuring device is used, before a thermal response test formally starts, the connected temperature measuring lead firstly extends into the buried pipe according to corresponding scales and the corresponding depth, so that the temperature of water in the buried pipe with a certain depth can be obtained, the temperature sensor is used for connecting the temperature measuring lead for measuring the temperature, more accurate and non-interference ground temperature data can be obtained, the operation difficulty in the actual temperature measuring process can be effectively and reliably solved, the temperature measuring device has the advantages of simple structure, firmness and durability, convenience in operation and the like, the non-interference ground temperature data with multiple depths can be collected, the temperature gradient distribution of the stratum can be obtained, the weighted average value of multiple numerical values of the ground temperature gradient distribution can be obtained, and the. In the design, the heat dissipation amount from summer to the underground is longer than the heat dissipation time of the heat extracted from the soil in winter, namely the soil heat recovery time can be calculated by the method, and the design of the air conditioning system is guided in the aspect of underground heat conduction.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (4)
1. A method for measuring the soil heat recovery capability through a thermal response test method is characterized in that: the method comprises the following steps:
the method comprises the following steps of firstly, obtaining the heat load of a building according to the design data of the building, and obtaining the power data of a single well according to a thermal response heating power calculation formula, wherein the thermal response heating power is the product of the heat exchange quantity per linear meter and the depth of the single well;
step two, according to the time set by the requirement, the calculated constant power and other achievable powers start a thermal response instrument to test, the actual power and other powers are simulated, the thermal response instrument operates for a period of time in a single-hole well, the total soil temperature displayed by the thermal response instrument is read after the heating operation is finished, and the temperature of each stratum is immediately measured by an interference-free ground temperature device;
step three, laying aside for a period of time and measuring the temperature of each stratum in real time;
and step four, obtaining related test data, processing the data to obtain the soil restoration capacity under different test conditions, namely the non-interference soil temperature measurement soil restoration capacity.
2. The method for measuring the soil heat recovery capability through the thermal response test method according to claim 1, wherein: the length of the standing time in the third step can be selected according to needs, and the longest standing time is the temperature recovery time of each stratum.
3. The method for measuring the soil heat recovery capability through the thermal response test method according to claim 1, wherein: the interference-free ground temperature device adopts a 300m temperature measuring lead, the bottom of the lead is connected with a PT100 temperature sensor and a counterweight, and a group of interference-free ground temperature devices are arranged upwards at certain intervals.
4. The method for measuring the soil heat recovery capability through the thermal response test method according to claim 1, wherein: the recovery capability of the soil measured without interference in the fourth step is that the soil with multiple groups of gradient depths is different from different T2Temperature recovery to a different T1The average rates of the plurality of groups of heat emitted outwards by the temperature can be verified by the average rate of the heat emitted measured by the thermal response tester, and are obtained by the following formula:
from T for a certain depth/total soil2Temperature recoveryTo T1Temperature difference of temperature:
ΔT＝(T2-T1)
wherein, T2-instantaneous certain depth/global ground temperature after heating; t is1After heating, standing for a period of time T and T1Same depth/overall ground temperature;
above depth/total soil from T2Temperature returns to T1Average recovery rate of temperature:
wherein, t is the standing time of the soil, namely the temperature recovery time;
above depth/total soil from T2Temperature returns to T1Heat dissipated outward by temperature:
c, soil specific heat capacity is similar to the whole well weighted average value at the same depth as the temperature measuring point; l-flow of circulating water in the underground pipe; ρ — density of water;
thus, the depth/total soil is from T2Temperature returns to T1Average rate of heat dissipated outward by temperature:
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| US4228511A (en) * | 1978-10-06 | 1980-10-14 | General Electric Company | System and method of power demand limiting and temperature control |
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| CN103363723A (en) * | 2013-07-25 | 2013-10-23 | 湖南大学 | Active recovery system and active recovery method for balancing heat extraction and heat removal of ground heat exchanger |
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