CN113607295A - Low-temperature air temperature and humidity measurement and calculation method - Google Patents
Low-temperature air temperature and humidity measurement and calculation method Download PDFInfo
- Publication number
- CN113607295A CN113607295A CN202110641629.4A CN202110641629A CN113607295A CN 113607295 A CN113607295 A CN 113607295A CN 202110641629 A CN202110641629 A CN 202110641629A CN 113607295 A CN113607295 A CN 113607295A
- Authority
- CN
- China
- Prior art keywords
- air
- temperature
- humidity
- low
- measuring
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000691 measurement method Methods 0.000 title claims abstract description 7
- 238000004364 calculation method Methods 0.000 title claims description 30
- 238000005259 measurement Methods 0.000 claims abstract description 68
- 238000000034 method Methods 0.000 claims abstract description 41
- 238000003303 reheating Methods 0.000 claims abstract description 6
- 238000010438 heat treatment Methods 0.000 claims description 52
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 30
- 238000005070 sampling Methods 0.000 claims description 25
- 238000004321 preservation Methods 0.000 claims description 24
- 238000011144 upstream manufacturing Methods 0.000 claims description 13
- 239000007788 liquid Substances 0.000 claims description 8
- 238000007689 inspection Methods 0.000 claims description 7
- 238000012544 monitoring process Methods 0.000 claims description 6
- 238000009834 vaporization Methods 0.000 claims description 3
- 230000008016 vaporization Effects 0.000 claims description 3
- 238000012545 processing Methods 0.000 claims description 2
- 230000033228 biological regulation Effects 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 claims 1
- 230000009123 feedback regulation Effects 0.000 claims 1
- 230000001502 supplementing effect Effects 0.000 description 9
- 239000000463 material Substances 0.000 description 7
- 230000008569 process Effects 0.000 description 6
- 239000000919 ceramic Substances 0.000 description 4
- 238000009413 insulation Methods 0.000 description 4
- 239000000047 product Substances 0.000 description 3
- 230000005855 radiation Effects 0.000 description 3
- 229920006395 saturated elastomer Polymers 0.000 description 3
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000004378 air conditioning Methods 0.000 description 2
- 238000009833 condensation Methods 0.000 description 2
- 230000005494 condensation Effects 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000005485 electric heating Methods 0.000 description 2
- 239000003063 flame retardant Substances 0.000 description 2
- 239000012774 insulation material Substances 0.000 description 2
- 229920002635 polyurethane Polymers 0.000 description 2
- 239000004814 polyurethane Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000009423 ventilation Methods 0.000 description 2
- 229920000742 Cotton Polymers 0.000 description 1
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- 239000004964 aerogel Substances 0.000 description 1
- 239000010425 asbestos Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
- 210000004209 hair Anatomy 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000011490 mineral wool Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 229910052895 riebeckite Inorganic materials 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/56—Investigating or analyzing materials by the use of thermal means by investigating moisture content
- G01N25/66—Investigating or analyzing materials by the use of thermal means by investigating moisture content by investigating dew-point
- G01N25/68—Investigating or analyzing materials by the use of thermal means by investigating moisture content by investigating dew-point by varying the temperature of a condensing surface
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
Landscapes
- Chemical & Material Sciences (AREA)
- General Physics & Mathematics (AREA)
- Physics & Mathematics (AREA)
- General Health & Medical Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Investigating Or Analyzing Materials Using Thermal Means (AREA)
Abstract
The invention belongs to the technical field of air temperature and humidity measurement, and particularly relates to a method for measuring and calculating low-temperature air temperature and humidity. The method realizes high-precision measurement of the wet bulb temperature and the enthalpy value of the low-temperature air, heats the sampled low-temperature air by a constant-humidity reheating method through a low-temperature air temperature and humidity measuring device, and calculates the temperature and humidity of the sampled low-temperature air according to the dry bulb temperature and the air pressure of the sampled low-temperature air, the dry bulb temperature of the heated air, the wet bulb temperature and the air pressure. The invention only relates to the measurement of two state point parameters, the measurement method is simple and easy to realize, the measurement of the low-temperature air humidity parameter has the advantage of high measurement precision, and the integrated accurate measurement of the air temperature and the air humidity under the low-temperature condition can be realized.
Description
Technical Field
The invention belongs to the technical field of air temperature and humidity measurement, and particularly relates to a method for measuring and calculating low-temperature air temperature and humidity.
Background
The ambient atmosphere we are exposed to is a mixture of dry air and water vapour, commonly referred to as humid air. Unlike the conventional concept of ambient temperature, the temperature in the drying, heating, air conditioning, cooling tower and other projects is generally referred to as the dry bulb temperature of the humid air, which can be measured directly. And physical quantities such as wet bulb temperature or relative humidity and absolute humidity (also called as absolute humidity content) of ambient atmosphere are generally adopted to represent humidity state parameters of the wet air, so that the analysis and calculation of the wet air thermodynamic process in the thermodynamic field are facilitated. Humidity parameters such as wet bulb temperature, relative humidity and absolute humidity can be used to represent the moisture content in air or the humidity of air, which are very important physical quantities that are difficult to measure accurately in the wet air state parameters.
The humidity measurement method of the air generally can obtain the relative humidity or absolute humidity parameter of the humid air by directly measuring the dry bulb temperature and the wet bulb temperature of the humid air and adopting a certain calculation method, also can directly measure the relative humidity parameter of the humid air by a measurement instrument, and can calculate and obtain other parameters of the humidity representation of the humid air according to the existing calculation formula.
The current method for measuring humidity parameters of humid air comprises the following steps:
1. the humidity measurement is carried out by utilizing the characteristic that substances such as fibers and hairs stretch and contract along with the change of air humidity, and the humidity measurement method has the advantages of simplicity, low cost and poor measurement accuracy.
2. The wet-dry bulb humidity method has the advantages that the precision is high, when the air temperature is 20-30 ℃, and the measurement error of the wet-dry bulb temperature is not more than 0.1 ℃, a wet-dry meter with a constant ventilation device can be identified as a second-class standard device for humidity measurement, and the measurement error is not more than +/-2% RH (relative humidity). However, since the saturated vapor pressure of water is an exponential function of temperature, the saturated vapor pressure of water at low temperature is far lower than the corresponding data at normal temperature, so that the wet-dry bulb humidity method for measuring the humidity of wet air is not applicable under the temperature condition lower than 0 ℃, and the measurement range is generally 5-40 ℃.
3. Dew point temperature method. The method carries out indirect measurement of humidity by measuring the dew point temperature of air and mainly comprises a cooling device, a dew-forming surface and a temperature sensor. The method has high measurement precision under the conditions of low temperature and low humidity, but the device is complex and has high cost, and the accurate control of the temperature of the condensation surface is difficult to realize.
4. Humidity sensitive humidity sensor method. The method has the advantages of quick response, small wet hysteresis and wide measurement range, the nominal measurement precision of the middle and low wet sections is +/-2% RH, and the nominal measurement precision of the high wet section is +/-4% RH. However, the third party test result shows that the accuracy is difficult to achieve even in the ventilation state of 20-30 ℃, and the measurement errors of the low-temperature section and the high-humidity section are difficult to guarantee. In addition, since the humidity sensor needs to be exposed to the environment to be measured for a long time, the humidity sensor is susceptible to contamination, which affects the accuracy and stability of the humidity sensor.
In the performance test of the refrigeration air-conditioning product, the measurement problem of the air temperature and humidity in a wide temperature range is often involved. The air humidity is usually measured at normal temperature by dry and wet bulb methods, and at low temperature by humidity-sensitive humidity sensors. Because the humidity-sensitive humidity sensor method cannot meet the problem of air humidity measurement accuracy in a low-temperature state, the humidity parameter test performed by the humidity-sensitive humidity sensor method at a low temperature is only used as an operation condition parameter and is not used for calculating the refrigerating and heating capacity.
With the continuous development of society, novel products such as various low-temperature heat pump units can be developed and applied, humidity parameters at low temperature need to be determined by calculation of basic performance of the products through an air enthalpy difference method after being tested, the existing humidity-sensitive humidity sensor is poor in stability and difficult to meet the precision requirement of low-temperature humidity measurement, the cost of a high-precision dew-point temperature sensor is increased by multiple times, and the device is complex and difficult to realize the precise measurement and control of the temperature of a dew condensation surface. Therefore, there is a strong need for a new measuring device to achieve accurate and stable measurement of the humidity of the low-temperature air.
Disclosure of Invention
In order to solve the technical problem, the invention provides a method for measuring and calculating the temperature and the humidity of low-temperature air, which can measure the humidity of a wet bulb of air below 0 ℃ with higher precision.
The method comprises the steps of heating sampled low-temperature air by a constant-humidity reheating method through a low-temperature air temperature and humidity measuring device, and calculating the temperature and humidity of the sampled low-temperature air according to the dry-bulb temperature and air pressure of the sampled low-temperature air and the dry-bulb temperature, wet-bulb temperature and air pressure of the heated air;
the low-temperature air temperature and humidity measuring device comprises an air channel and an air heater for dividing the air channel into an upstream air channel and a downstream air channel, sampling low-temperature air enters from the upstream air channel, is heated by the air heater and then flows into the downstream air channel, and a constant-humidity reheating environment is formed in the upstream air channel and the downstream air channel.
Preferably, a first air pressure measuring instrument and a first dry bulb temperature measuring instrument are arranged in the upstream air channel, and air pipes of the upstream air channel section jointly form a sampling air measuring assembly; a second dry bulb temperature measuring instrument and an air wet bulb temperature measuring instrument are arranged in the downstream air channel, the second dry bulb temperature measuring instrument is electrically connected with the air heater, and the second dry bulb temperature measuring instrument, the air wet bulb temperature measuring instrument and an air pipe of the downstream air channel section jointly form a heated air measuring assembly; the tail end of the downstream air duct is also connected with a fan for guiding the flow of sampling low-temperature air.
Preferably, the low-temperature air temperature and humidity measuring device further comprises a heat preservation box body and an air sampler, wherein the heat preservation box body is hermetically covered on the outer sides of the air heater, the heated air measuring assembly and the fan; the air sampler is connected with the upstream end of the sampling air measurement assembly for air sampling.
Preferably, the fan is arranged in the heat preservation box body, is connected to the outer side of the heat preservation box body through an air outlet pipe (81) and is used for discharging measured heated air.
The heat preservation box body is made of heat preservation materials with the thickness larger than 75mm and the heat conductivity coefficient lower than 0.23W/m.K, such as double-sided color steel plates or flame-retardant polyurethane storehouses; the air pipe arranged in the heat preservation box body is wrapped with materials for isolating heat radiation, and comprises three types of porous materials, heat reflecting materials and vacuum materials, such as traditional heat insulation materials of glass fiber, asbestos, rock wool, silicate and the like or novel heat insulation materials of aerogel felt, vacuum plates and the like.
Preferably, the sampling air measuring assembly is further provided with a first flow mixer at the front end of the air pipe thereof, and the heating air measuring assembly is further provided with a second flow mixer at the front end of the air pipe thereof, near the air heater.
Preferably, the air wet bulb thermometer comprises an air wet bulb thermometer body and a water supplementing cup, and the upper space of the liquid level in the water supplementing cup is communicated with the air channel and is used for maintaining the wet environment in the air channel; one end of the air-wet ball thermodetector body is inserted below the liquid level of the water supplementing cup, and the other end of the air-wet ball thermodetector body extends into the air duct for measurement.
Preferably, a heat leakage compensation device is further arranged in the heat preservation box body, the heat leakage compensation device is composed of a heating lamp and a thermocouple, when the temperature of the thermocouple is lower than 20 ℃, the heating lamp is turned on and heats the environment in the heat preservation box body, and when the temperature of the thermocouple is higher than 25 ℃, the heating lamp is turned off.
Preferably, the heated air measuring assembly further comprises a second air pressure measuring instrument and an air speed measuring instrument, the air speed measuring instrument is electrically connected with the fan, and the fan feeds back and adjusts the operating power of the fan according to the received measuring result of the air speed measuring instrument, so as to adjust the air speed in the air duct.
Preferably, the method for measuring and calculating the temperature and humidity of the low-temperature air comprises the following steps:
s1, starting a fan, wherein the fan works to generate suction force to enable low-temperature air to enter an upstream air channel through an air sampler, and to flow into a downstream air channel after being heated by an air heater;
s2, the heated air measurement assembly works, and the fan receives the wind speed value measured by the second air pressure gauge and adjusts the operating frequency of the fan until the wind speed is within the range of 5m/s +/-1 m/s; the air heater receives a temperature result measured by the second dry bulb temperature measuring instrument, and the power of the air heater is adjusted until the air temperature in the downstream air channel reaches a set temperature value;
s3, the sampling air measurement assembly works to measure the pressure P before heating of the sampled low-temperature air1And the dry bulb temperature t before heating1While the heated air pressure P is measured by the heated air measurement assembly2Air dry bulb temperature t after heating2And the heated air wet bulb temperature tw2；
S4, according to the result measured in the step S3, calculating the absolute humidity d of the saturated water vapor of the heated air according to an absolute humidity calculation formula2And according to the absolute humidity d of saturated water vapor of the air before heating1＝d2Calculating the wet bulb temperature t of the sampled low-temperature airw1(ii) a Saturated water vapor absolute humidity d of the pre-heating air1And wet bulb temperature tw1Namely the temperature and humidity data of the sampled measured low-temperature air.
The absolute humidity calculation formula is as follows:
the wet bulb temperature t of the sampled low temperature airw1The calculation formula is as follows:
in the formula (d)s(tw2) For heating the air at the wet bulb temperature tw2Saturated humidity in kg (water vapor)/kg (dry air), r (t)w2) For heating the air at the wet bulb temperature tw2Latent heat of vaporization in kJ/kg;
pre-heating pressure P of low-temperature air to be sampled1And the dry bulb temperature t before heating1And d obtained by calculation2The temperature and humidity data of the sampled measured low-temperature air can be obtained by substituting the temperature and humidity data into the calculation formula.
Preferably, the heat preservation box body is provided with an inspection door and a monitoring screen, the inspection door is provided with an observation window, and the bottom of the heat preservation box body is also provided with universal wheels.
Preferably, the first air pressure gauge, the second air pressure gauge, the first dry bulb temperature gauge, the second dry bulb temperature gauge and the air wet bulb temperature gauge are all electrically connected with the same PLC processing system, and output measurement data and temperature and humidity calculation results to the monitoring screen.
The invention has the beneficial effects that:
1. the invention only relates to the measurement of two state point parameters, namely the dry bulb temperature and the air pressure of sampled low-temperature air and the dry bulb temperature and the wet bulb temperature and the air pressure of heated air, and the measurement method is simple and easy to realize. Specifically, the measurement accuracy of the humidity parameter of the low-temperature wet air is improved by improving the measurement accuracy of the humidity parameter of the low-temperature wet air and reducing the deviation between the wet air wet bulb temperature obtained by measurement and the adiabatic saturation temperature, and the deviation between the wet air wet bulb temperature obtained by measurement and the adiabatic saturation temperature is reduced. Meanwhile, when subsequent calculation is carried out, the difference between the absolute saturation temperature and the wet bulb temperature in the physical sense can be ignored, the calculation process is simplified by utilizing the fact that the absolute saturation temperature and the wet bulb temperature are very close to each other, and a measurement result with higher accuracy is obtained. Finally, the integrated accurate measurement of the air temperature and humidity under the low-temperature condition is realized.
2. According to the invention, the air pipe connected with the heater is wrapped with the thermal radiation prevention material, so that the influence of the air heater in the insulation box on the measurement precision of the heated air measurement assembly can be effectively prevented. The setting of insulation box has improved the security and the convenience of this device operation under low temperature environment. Particularly, the water replenishing cup is arranged inside the heat preservation box body, so that automatic water replenishing of the air wet bulb temperature measuring instrument can be realized, and the condition that the air wet bulb temperature measuring instrument cannot be used due to frost cracking under the low-temperature condition is avoided.
3. The invention can adopt the conventional instrument to realize the measurement of the low-temperature air humidity, thus greatly reducing the investment and maintenance cost; the PLC system is arranged, so that the device integrates data measurement, calculation and output functions, and can be independently applied to various occasions. And through calculating the measurement data, the measurement of other state parameters of the sampled air, such as relative humidity, dew point temperature and the like, can also be realized.
4. According to the invention, the constant humidity reheating method is adopted to heat the low-temperature air and then measure all parameters, but the direct measurement of the electric heating quantity is not needed, so that the measurement process is simplified, and the measurement link generating errors is reduced; meanwhile, the equal-humidity heating process of air is realized through adjustable electric heating, and the theoretical range of the equal-humidity heating process is only limited by the range of the temperature sensor at the low temperature side.
Drawings
FIG. 1 is a schematic diagram of the method for measuring the temperature and humidity of low temperature air according to the present invention;
FIG. 2 is a schematic view of the apparatus for measuring the temperature and humidity of low-temperature air according to the present invention;
FIG. 3 is a cross-sectional side view of the low temperature air temperature and humidity measuring device of the present invention;
FIG. 4 is a side view of the low temperature air humidity measuring device of the present invention;
fig. 5 is an isometric view of a cryogenic air temperature and humidity measurement device of the present invention.
The notations in the figures have the following meanings:
10-air sampler
20-sampling air measurement assembly 21-first air pressure gauge 22-first dry bulb thermometer
30-heated air measurement Assembly 31-second air pressure gauge 32-second Dry bulb thermometer
33-air wet bulb thermodetector 331-water supplement cup 34-wind speed measuring instrument 40-air heater
50-air duct 60-heat preservation box 61-inspection door 611-observation window 62-monitoring screen
71-first mixer 72-second mixer 80-fan 81-air outlet pipe
90-heat leakage compensation device 100-air return opening 101 of machine to be tested-working condition environment
Detailed Description
The technical scheme of the invention is described in more detail by combining the embodiment and the attached drawings:
example 1
A low-temperature air temperature and humidity measuring device comprises an air channel 50 and an air heater 40 for dividing the air channel 50 into an upper part and a lower part, wherein a first air pressure measuring instrument 21 and a first dry bulb temperature measuring instrument 22 are sequentially arranged in the upper air channel along the air flow direction, and form a sampling air measuring assembly 20 together with an air pipe of an upper air channel section; a second dry bulb temperature measuring instrument 32 and an air wet bulb temperature measuring instrument 33 are arranged in the downstream air channel along the air flow direction, and form a heated air measuring assembly 30 together with an air pipe of the downstream air channel section.
The low-temperature air temperature and humidity measuring device also comprises a heat preservation box body 60 and an air sampler 10, wherein the heat preservation box body 60 is hermetically covered on the outer sides of the air heater 40 and the fan 80 of the heated air measuring assembly 30; air sampler 10 is connected to the upstream end of sampling air measurement assembly 20 for air sampling, in this embodiment, air sampler 10 is a sampling rake.
The sampling air measuring assembly 20 is further provided with a first flow mixer 71 at the front end of the air duct thereof, and the heating air measuring assembly 30 is further provided with a second flow mixer 72 at the front end of the air duct thereof, near the air heater 40. The mixer is used for ensuring that the temperature and the humidity of the air flowing into the sampling air measuring assembly 20 and the heating air measuring assembly 30 are uniform, and reducing the measuring error.
The tail end of the heated air measuring assembly 30 is connected with a fan 80, the heated air measuring assembly 30 further comprises a second air pressure gauge 31 and an air speed measuring gauge 34, the air speed measuring gauge 34 is arranged close to the second mixer 72, the air speed measuring gauge 34 is electrically connected with the fan 80, and the fan 80 receives the measuring result of the air speed measuring gauge 34 and adjusts the operating frequency of the fan 80, so that the air speed in the air duct 50 is constant. Since the wind speed has an influence on the pressure and the heat transfer, the wind speed regulated by the fan in the invention is preferably 5 +/-1 m/s. The fan 80 is disposed in the heat insulating box 60 and connected to the outside of the heat insulating box 60 through an air outlet pipe 81 for discharging the measured heated air.
The second dry bulb thermometer 32 is electrically connected to an air heater 40. In this embodiment, the air heater 40 is a fin-type electric heater, and the temperature of the heated air dry bulb is controllable by feedback adjustment of the measured temperature of the second dry bulb thermometer 32, so as to realize an equal-humidity heating process of the measured air. Specifically, the temperature measured by the second dry bulb thermometer 32 is collected in real time by the programmable logic controller, and is continuously compared with a set target temperature, and an instruction is sent to the power regulator to adjust the running current value of the air heater 40, so that the temperature of the heated air dry bulb is controllable.
The air wet bulb temperature measuring instrument 33 comprises an air wet bulb temperature measuring instrument body, a water supplementing cup 331 and a hydraulic water supplementing tank, the upper space of the liquid level in the water supplementing cup 331 is communicated with the air duct 50 and used for keeping the wet environment in the air duct 50, the liquid level in the water supplementing cup 331 is kept constant by the hydraulic water supplementing tank and liquid in the water supplementing cup 331 is prevented from entering the air duct 50.
One end of the air-wet bulb thermodetector body is inserted below the liquid level of the water replenishing cup 33, and the other end of the air-wet bulb thermodetector body wraps the wet cotton yarn and extends into the air duct 50 to be used for measuring wet bulb temperature parameters of air flowing through.
The heat preservation box body 60 is made of heat preservation materials with the thickness larger than 75mm and the heat conductivity coefficient lower than 0.23W/m.K, such as double-sided color steel plates or flame-retardant polyurethane storehouses; the air pipe arranged in the heat insulation box body 60 is coated with a material for isolating heat radiation.
The heat-insulating box 60 is provided with an inspection door 61 for facilitating installation and debugging of each device, and the inspection door 61 is provided with an observation window 611. The thermal insulation box 60 is also provided with a monitoring screen 62. In this embodiment, the first air pressure gauge 21, the second air pressure gauge 31, the first dry bulb temperature gauge 22, the second dry bulb temperature gauge 32, and the air wet bulb temperature gauge 33 are all electrically connected to the same data acquisition device, the data acquisition device uses a relay output type PLC as a control core, and an analog input and an analog output module are configured, the PLC system collects all measured data electrical signals, the operation is performed through an internal program, and finally, each measured data and a temperature and humidity measurement result are output to the monitor 62.
The bottom of the heat preservation box body 60 can be provided with universal wheels to facilitate movement.
In order to avoid the influence of box body heat leakage on the measurement of the temperature of the dry and wet bulb, a heat leakage compensation device 90 is further arranged in the heat preservation box body 60, the heat leakage compensation device 90 consists of a ceramic heating lamp and a thermocouple, a measured temperature signal of the thermocouple is introduced into a programmable logic controller through an analog quantity acquisition module, and the measured temperature signal is judged and the on-off of the ceramic heating lamp is controlled through program editing and comparison instructions. When the temperature of the thermocouple is lower than 20 ℃, a control signal is output to turn on the ceramic heating lamp to heat the environment in the heat preservation box body 60, and when the temperature of the thermocouple is higher than 25 ℃, the control signal is stopped being output to turn off the ceramic heating lamp.
Example 2
A method for measuring and calculating the temperature and the humidity of low-temperature air comprises the following steps:
s1, starting a fan, wherein the fan works to generate suction force to enable low-temperature air to enter an upstream air channel through an air sampler, and to flow into a downstream air channel after being heated by an air heater;
s2, the heated air measuring assembly works, and the fan receives the wind speed value measured by the second air pressure gauge 31 and adjusts the operating frequency of the fan 80 until the wind speed is within the range of 5m/s +/-1 m/s; the air heater receives the temperature result measured by the second dry bulb thermodetector 32, and adjusts the power of the air heater until the air temperature in the downstream air channel reaches the set temperature value;
s3, the sampling air measurement component 20 works, and the first air pressure gauge 21 measures the pressure P before heating of the sampling air1The first dry bulb thermometer 22 measures the air temperature t before heating1While the heated air pressure P is measured by the heated air measurement assembly 302Air dry bulb temperature t after heating2And the heated air wet bulb temperature tw2；
S4, calculating the relative humidity of the heated air according to the absolute humidity calculation formula and the result measured in the step S3Degree of rotation
The calculation process is as follows: first, the absolute humidity d of the humid air is calculated2The absolute humidity calculation formula is as follows:
in the formula (d)2The absolute humidity value of saturated water vapor of heated air is given in kg (water vapor)/kg (dry air), ds(tw2) For heating the air at the wet bulb temperature tw2Saturated humidity in kg (water vapor)/kg (dry air), r (t)w2) For heating the air at the wet bulb temperature tw2Latent heat of vaporization in kJ/kg;
r(tw2)＝-2.4114tw2+2501.7 (2)
in the formula, Ps(tw2) For heating the air at the wet bulb temperature tw2The lower corresponds to the saturated steam pressure in Pa.
According to the measured wet bulb temperature t of the heated wet airw2Is calculated by combining the values of the formulas (2) to (4) to obtain r (t)w2)，ds(tw2)，Ps(tw2) Parameter, based on the measured value t of the dry bulb temperature of the heated humid air2Obtaining the value d of the absolute moisture content of the heated humid air by calculation in combination with the formula (1)2。
From the principle that the absolute moisture content of the moist air is constant before and after heating, d2I.e. the absolute moisture content of the air before sampling and heating.
r(tw1)＝-2.4114tw1+2501.7 (7)
Ps(tw1) Is tw1Saturated steam pressure at temperature, in Pa;
substituting (5) to (7) into the formula (8) can obtain:
the pre-heating pressure P of the sampled air1And the dry bulb temperature t before heating1And d obtained by calculation2The temperature and humidity data of the sampled measured low-temperature air can be obtained by substituting the temperature and humidity data into the calculation formula.
The above formula utilizes the principle that the absolute moisture content is kept unchanged before and after heating, and the difference between the wet bulb temperature of the wet air obtained by measurement and the adiabatic saturation temperature is reduced by the device, so that the difference between the absolute saturation temperature and the wet bulb temperature in the physical sense can be ignored in the calculation process, the calculation process is simplified by utilizing the numerical value close to the absolute saturation temperature and the wet bulb temperature, and the measurement result with higher accuracy is obtained.
Example 3
In a working condition 101 with stable operation, the air sampler 10 of the low-temperature air temperature and humidity sampling and measuring device of the present invention is placed at the air return opening 100 of the machine to be tested, the blower 80 is started, and the measurement is performed according to the procedure of embodiment 2.
At a certain time, the wind speed measuring instrument 34 measures the current wind speed to be 5m/s, the sampled air measurement assembly 20 measures the pre-heating pressure P of the sampled low temperature air1＝100510PaAir temperature t before heating1-10 ℃ under vacuum; heated air pressure P measured by heated air measurement assembly 302＝100360PaAir dry bulb temperature t after heating123.4 ℃, and the wet bulb temperature t of heated airw2Not higher than 9.1 ℃. The measurement accuracy of the sensors of the dry bulb thermometers and the wet bulb thermometers used in the device is +/-0.1 ℃.
In this embodiment, the enthalpy h of the sampled low temperature air can be obtained by using the known data1Relative humidity, dew point temperature, etc. Such as:
substituting equation (5) into equation (10) yields:
h1＝1.005t1+(2501+1.846t1)d1(12) substituting the parameters into equations (11) and (12) to obtain enthalpy value h of low-temperature air before sampling1And relative humidity parameter
In the embodiment, the enthalpy value h of the sampled low-temperature air is calculated16.493KJ/Kg, 80.71% RH relative humidity, dew point-12.18 deg.C.
The above embodiments are only used to illustrate the technical solutions of the present invention, and do not limit the present invention; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that: any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A temperature and humidity measurement and calculation method for low-temperature air is characterized in that the method heats sampled low-temperature air by a constant humidity reheating method through a low-temperature air temperature and humidity measurement device, and calculates the temperature and humidity of the sampled low-temperature air according to the dry bulb temperature and the air pressure of the sampled low-temperature air and the dry bulb temperature and the wet bulb temperature and the air pressure of the heated air;
the low-temperature air temperature and humidity measuring device comprises an air duct (50) and an air heater (40) for dividing the air duct (50) into an upper portion and a lower portion, sampling low-temperature air enters from the upper air duct, is heated by the air heater (40) and then flows into the lower air duct, and a constant-humidity reheating environment is formed in the upper air duct and the lower air duct.
2. The method for measuring and calculating the temperature and the humidity of the low-temperature air according to claim 1, wherein a first air pressure gauge (21) and a first dry bulb temperature gauge (22) are arranged in the upstream air duct, and the first air pressure gauge and an air duct of the upstream air duct section form a sampling air measuring assembly (20); a second dry bulb temperature measuring instrument (32) and an air wet bulb temperature measuring instrument (33) are arranged in the downstream air channel, and the second dry bulb temperature measuring instrument and an air pipe of the downstream air channel section form a heated air measuring assembly (30) together; the tail end of the downstream air duct is also connected with a fan (80) for guiding the air flow.
3. The method for measuring and calculating the temperature and humidity of the low-temperature air according to claim 2, wherein the device for measuring the temperature and humidity of the low-temperature air further comprises a heat preservation box body (60) and an air sampler (10), wherein the heat preservation box body (60) is hermetically covered on the outer sides of the air heater (40), the heated air measuring assembly (30) and the fan (80); the air sampler (10) is connected with the upstream end of the sampling air measurement component (20) and used for air sampling, and the fan (80) adopts frequency conversion regulation.
4. The method for measuring and calculating the temperature and humidity of the low-temperature air according to claim 2, wherein the sampling air measuring assembly (20) is further provided with a first flow mixer (71) at the air inlet end of the air duct, and the heating air measuring assembly (30) is further provided with a second flow mixer (72) at the air inlet end of the air duct and close to the air heater (40).
5. The method for measuring and calculating the temperature and humidity of the low-temperature air according to claim 2, wherein the air wet bulb thermometer (33) comprises an air wet bulb thermometer body and a water replenishing cup (331), and a space above a liquid level in the water replenishing cup (331) is communicated with the air duct (50) and used for maintaining a wet environment in the air duct (50); one end of the air-wet ball temperature measuring instrument body is inserted below the liquid level of the water replenishing cup (33), and the other end of the air-wet ball temperature measuring instrument body extends into the air duct (50) for measurement.
6. The method for measuring and calculating the temperature and humidity of the low-temperature air according to claim 3, wherein a heat leakage compensation device (90) is further arranged in the heat preservation box body (60), the heat leakage compensation device (90) comprises a heating lamp and a thermocouple, the heating lamp is turned on to heat the environment in the heat preservation box body (60) when the temperature of the thermocouple is lower than 20 ℃, and the heating lamp is turned off when the temperature of the thermocouple is higher than 25 ℃.
7. The method for measuring and calculating the temperature and humidity of the low-temperature air according to any one of claims 2 to 6, wherein the heated air measuring assembly (30) further comprises a second air pressure measuring instrument (31) and an air speed measuring instrument (34), the air speed measuring instrument (34) is electrically connected with the fan (80), and the fan (80) performs feedback regulation according to the received measurement result of the air speed measuring instrument (34) for adjusting the air speed in the air duct (50).
8. The method for measuring and calculating the temperature and the humidity of the low-temperature air according to claim 7, comprising the following steps of:
s1, starting a fan (80), wherein the fan works to generate suction force to enable low-temperature air to enter an upstream air channel and flow into a downstream air channel after being heated by an air heater;
s2, the heated air measurement assembly (30) works, and the fan (80) receives the wind speed value measured by the second air pressure gauge (31) and adjusts the operating frequency of the fan (80) until the wind speed is within 5m/s +/-1 m/s; the air heater (40) receives the temperature result measured by the second dry bulb temperature measuring instrument (32), and the power of the air heater (40) is adjusted until the air temperature in the downstream air channel reaches a set temperature value;
s3, the sampling air measurement component (20) works to measure the pressure P before heating of the sampled low-temperature air1And the dry bulb temperature t before heating1While the heated air measuring assembly (30) measures the heated air pressure P2Air dry bulb temperature t after heating2And the heated air wet bulb temperature tw2；
S4, according to the result measured in the step S3, calculating the absolute humidity d of the saturated water vapor of the heated air according to an absolute humidity calculation formula2And according to the absolute humidity d of saturated water vapor of the air before heating1＝d2Calculating the wet bulb temperature t of the sampled low-temperature airw1(ii) a Saturated water vapor absolute humidity d of the pre-heating air1And wet bulb temperature tw1Namely the temperature and humidity data of the sampled measured low-temperature air.
9. The method for measuring and calculating the temperature and humidity of the low-temperature air according to claim 8, wherein the absolute humidity calculation formula is as follows:
the wet bulb temperature t of the sampled low temperature airw1The calculation formula is as follows:
in the formula (d)s(tw2) For heating the air at the wet bulb temperature tw2Saturated humidity in kg (water vapor)/kg (dry air), r (t)w2) For heating the air at the wet bulb temperature tw2Latent heat of vaporization in kJ/kg;
pre-heating pressure P of low-temperature air to be sampled1And the dry bulb temperature t before heating1And d obtained by calculation2The temperature and humidity data of the sampled measured low-temperature air can be obtained by substituting the temperature and humidity data into the calculation formula.
10. The method for measuring and calculating the temperature and humidity of the low-temperature air according to claim 8, wherein the heat-insulating box (60) is provided with an inspection door (61) and a monitoring screen (62), the inspection door (61) is provided with an observation window (611), and the first air pressure gauge (21), the second air pressure gauge (31), the first dry bulb temperature gauge (22), the second dry bulb temperature gauge (32) and the air wet bulb temperature gauge (33) are all electrically connected with the same PLC processing system and output the measurement data and the temperature and humidity calculation result to the monitoring screen (62).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110641629.4A CN113607295A (en) | 2021-06-09 | 2021-06-09 | Low-temperature air temperature and humidity measurement and calculation method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110641629.4A CN113607295A (en) | 2021-06-09 | 2021-06-09 | Low-temperature air temperature and humidity measurement and calculation method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN113607295A true CN113607295A (en) | 2021-11-05 |
Family
ID=78303504
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110641629.4A Pending CN113607295A (en) | 2021-06-09 | 2021-06-09 | Low-temperature air temperature and humidity measurement and calculation method |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113607295A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113587976A (en) * | 2021-06-09 | 2021-11-02 | 合肥通用机械研究院有限公司 | Wide temperature range air temperature and humidity sampling and measuring device |
| CN116931629A (en) * | 2023-09-18 | 2023-10-24 | 湖南朗赫科技有限公司 | Control method, system and storage medium for preventing indoor moisture regain and dew condensation |
Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05288375A (en) * | 1992-04-10 | 1993-11-02 | Kubota Corp | Method and apparatus for detecting humidity of humidifier |
| CN102418966A (en) * | 2011-12-19 | 2012-04-18 | 东南大学 | Air treatment device and air treatment method |
| JP2012211825A (en) * | 2011-03-31 | 2012-11-01 | Suga Test Instr Co Ltd | Absolute humidity-based temperature and humidity adjusting control system and testing apparatus using the same |
| CN102937490A (en) * | 2012-10-18 | 2013-02-20 | 浙江省检验检疫科学技术研究院 | Air conditioner refrigerating capacity and heating capacity testing method and air pipe box heat meter |
| CN203203953U (en) * | 2013-05-03 | 2013-09-18 | 上海纺织节能环保中心 | Combination box type moisture content measuring device |
| CN104730284A (en) * | 2013-12-24 | 2015-06-24 | 格力电器（合肥）有限公司 | Sampling wind speed monitoring device and enthalpy difference method experiment detection equipment with same |
| CN104728934A (en) * | 2013-12-20 | 2015-06-24 | 丰田自动车株式会社 | Air conditioning device and air conditioning control method |
| CN109946125A (en) * | 2019-04-28 | 2019-06-28 | 深圳国技仪器有限公司 | Measurement with wet gas temperature and humidity sampling apparatus |
| CN209355986U (en) * | 2019-02-28 | 2019-09-06 | 中国气象局气象探测中心 | A kind of outfield ventilation temperature moisture measurement standard |
| US20190310212A1 (en) * | 2016-08-26 | 2019-10-10 | Hitachi Automotive Systems, Ltd. | Thermal humidity measuring device |
| CN110488894A (en) * | 2019-07-31 | 2019-11-22 | 中国电器科学研究院股份有限公司 | A kind of aerial temperature and humidity test device and the method using its progress Temperature and Humidity Control |
| CN111443107A (en) * | 2020-05-13 | 2020-07-24 | 上海佐竹冷热控制技术有限公司 | Temperature and humidity measuring device and measuring method |
| CN113587976A (en) * | 2021-06-09 | 2021-11-02 | 合肥通用机械研究院有限公司 | Wide temperature range air temperature and humidity sampling and measuring device |
-
2021
- 2021-06-09 CN CN202110641629.4A patent/CN113607295A/en active Pending
Patent Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05288375A (en) * | 1992-04-10 | 1993-11-02 | Kubota Corp | Method and apparatus for detecting humidity of humidifier |
| JP2012211825A (en) * | 2011-03-31 | 2012-11-01 | Suga Test Instr Co Ltd | Absolute humidity-based temperature and humidity adjusting control system and testing apparatus using the same |
| CN102418966A (en) * | 2011-12-19 | 2012-04-18 | 东南大学 | Air treatment device and air treatment method |
| CN102937490A (en) * | 2012-10-18 | 2013-02-20 | 浙江省检验检疫科学技术研究院 | Air conditioner refrigerating capacity and heating capacity testing method and air pipe box heat meter |
| CN203203953U (en) * | 2013-05-03 | 2013-09-18 | 上海纺织节能环保中心 | Combination box type moisture content measuring device |
| CN104728934A (en) * | 2013-12-20 | 2015-06-24 | 丰田自动车株式会社 | Air conditioning device and air conditioning control method |
| CN104730284A (en) * | 2013-12-24 | 2015-06-24 | 格力电器（合肥）有限公司 | Sampling wind speed monitoring device and enthalpy difference method experiment detection equipment with same |
| US20190310212A1 (en) * | 2016-08-26 | 2019-10-10 | Hitachi Automotive Systems, Ltd. | Thermal humidity measuring device |
| CN209355986U (en) * | 2019-02-28 | 2019-09-06 | 中国气象局气象探测中心 | A kind of outfield ventilation temperature moisture measurement standard |
| CN109946125A (en) * | 2019-04-28 | 2019-06-28 | 深圳国技仪器有限公司 | Measurement with wet gas temperature and humidity sampling apparatus |
| CN110488894A (en) * | 2019-07-31 | 2019-11-22 | 中国电器科学研究院股份有限公司 | A kind of aerial temperature and humidity test device and the method using its progress Temperature and Humidity Control |
| CN111443107A (en) * | 2020-05-13 | 2020-07-24 | 上海佐竹冷热控制技术有限公司 | Temperature and humidity measuring device and measuring method |
| CN113587976A (en) * | 2021-06-09 | 2021-11-02 | 合肥通用机械研究院有限公司 | Wide temperature range air temperature and humidity sampling and measuring device |
Non-Patent Citations (4)
| Title |
|---|
| YONGPING HUANG: "A Method to Measure Humidity Based on Dry-Bulb and Wet-Bulb Temperatures", RESEARCH JOURNAL OF APPLIED SCIENCES, ENGINEERING AND TECHNOLOGY, 10 September 2013 (2013-09-10) * |
| 茆文杰: "双加热湿度传感 器及其校验系统设计", 中国优秀硕士学位论文全文数据库信息科技辑, no. 2, 15 February 2021 (2021-02-15) * |
| 薛相美: "干湿球法测量相对湿度的误差分析", 制冷与空调, vol. 2021, no. 05, 31 October 2021 (2021-10-31) * |
| 袁朝阳: "0℃以下湿球温度测量法及实验验证", 轻工机械, vol. 37, no. 4, 31 August 2019 (2019-08-31) * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113587976A (en) * | 2021-06-09 | 2021-11-02 | 合肥通用机械研究院有限公司 | Wide temperature range air temperature and humidity sampling and measuring device |
| CN113587976B (en) * | 2021-06-09 | 2024-04-09 | 合肥通用机械研究院有限公司 | Wide temperature range air temperature humidity sampling measurement device |
| CN116931629A (en) * | 2023-09-18 | 2023-10-24 | 湖南朗赫科技有限公司 | Control method, system and storage medium for preventing indoor moisture regain and dew condensation |
| CN116931629B (en) * | 2023-09-18 | 2024-01-12 | 湖南朗赫科技有限公司 | Control method, system and storage medium for preventing indoor moisture regain and dew condensation |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN113607295A (en) | Low-temperature air temperature and humidity measurement and calculation method | |
| CN104034625B (en) | One-dimensional heat and moisture transmission characteristic parameter measurement testing stand | |
| US4221058A (en) | Humidity responsive control for dryers | |
| CN110488894B (en) | Air temperature and humidity testing device and method for controlling temperature and humidity by using same | |
| JP3210843B2 (en) | How to measure blast furnace moisture | |
| CN111443107A (en) | Temperature and humidity measuring device and measuring method | |
| CN113587976B (en) | Wide temperature range air temperature humidity sampling measurement device | |
| CN101118444A (en) | Method for controlling air humidity of humiture test box and structure thereof | |
| KR20210044710A (en) | Test chamber and method for conditioning air | |
| US4461167A (en) | Psychrometer for measuring the humidity of a gas flow | |
| CN105784926B (en) | High wet gas current water capacity measurement apparatus and method | |
| CN112557240A (en) | Calibration device and method for flue gas humidity tester | |
| US20110094292A1 (en) | Apparatus for air property measurement | |
| JPH0350978B2 (en) | ||
| Zvizdic et al. | New primary dew-point generators at HMI/FSB-LPM in the Range from− 70° C to+ 60° C | |
| CN211906105U (en) | Environmental chamber | |
| JPS6141944A (en) | Gas sampling system | |
| CN106647898A (en) | Gas temperature, humidity and VOC concentration adjusting device and method | |
| JP3608655B2 (en) | Refrigeration capacity test method and apparatus | |
| CN220230579U (en) | Negative temperature relative humidity measuring device for environmental test | |
| RU2395824C1 (en) | Device to calibrate natural gas hydrometre | |
| WO2010125998A1 (en) | Vapor measurement device | |
| Carrington et al. | Calorimeter measurements of a heat pump dehumidifier: influence of evaporator air flow | |
| JPS61110042A (en) | Humidity measuring apparatus | |
| CN104914901B (en) | The miniature volatile organic matter that well-balanced adjustment can be carried out to the epidemic disaster and flow of each branch road discharges cabin system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |