CN100427936C - High-temperature air temperature and humidity measuring method - Google Patents

Abstract

The present invention relates to a high-temperature measuring method of the temperature and the humidity of air, which belongs to the technical field of the measurement of the parameters of the states of the air. The present invention is characterized in that the temperature of the air after a mixing process can be controlled within the measuring range of a conventional temperature and humidity instrument by adjusting the mixed-wind ratio of the high-temperature air to the low-temperature air, the humidity and the parameter of each state of the measured high-temperature air are calculated by the measurement of the dry bulb temperature of the high-temperature air and the dry and wet bulb temperature of the low-temperature air and mixed wind and the relation of the heating-power property of the wet air, and the humidity of the high-temperature air can be measured by the conventional temperature and humidity instrument. The high-temperature measuring method of the temperature and the humidity of air only needs to measure the dry and wet bulb temperature of the air and adjust the mixed-wind proportion of cold wind and hot wind and does not need to directly measure the mixed-wind ratio. The high-temperature measuring method of the temperature and the humidity of air can measure the humidity of the high-temperature air, and compared with the prior art, the high-temperature measuring method of the temperature and the humidity of air has the advantages of simple measuring method, high accuracy, low measuring cost, easy operation and easy realization.

Description

A kind of high temperature air humidity measuring method

Technical field

The present invention relates to a kind of high temperature air humidity measurement method, especially the state parameter of high temperature low humidity surrounding air is measured, and belongs to the air status parameter field of measuring technique.

Background technology

Air humidity be characterize water in air vapour content what or air do wet degree, it is extremely important and be difficult to accurately measure physical quantity in the air status parameter.The wet ability that definitely contains of air increases with the rising of air themperature, under the condition of high temperature more than 100 ℃, even it is very little that the relative humidity of air differs, but the difference of its absolute moisture content may be very big, therefore for high temperature air, the precision of its moisture measurement should be weighed with the measuring accuracy index of absolute moisture content.Measurement to air humidity at present mainly contains following several method: one, utilize materials such as hair, fiber to change the water capacity that the characteristic of stretching is measured air with surrounding air humidity.This measuring method is simple, and cost is low; But it is narrow to measure range, and precision is low, and maintenance management process complexity (Cheng Qifan, air humidity and measuring method thereof, Liaoning meteorology, 1996, (4): 36).Two, psychrometer: this method relative humidity measurement precision in range ability is higher, can reach ± 2%～± 3%RH; But its be applicable to gas humidity in 0 ℃～85 ℃ temperature ranges measure (Humidity MeasurementTechnology.http: //www.testo.de/US/lig/upload/mwmlus_1034594054750_1.pdf).Three, dew-point hygrometer: this method is measured the humidity of air indirectly by the dewpoint temperature of measuring air, mainly is made up of cooling device, dewfall face and temperature sensor.This method measuring accuracy under the low temperature and low humidity condition is higher; But this measuring method expense height, device is complicated, for guaranteeing the close dew temperature of minute surface, need accurately control simultaneously, seldom uses (Cheng Qifan, air humidity and measuring method thereof, Liaoning meteorology, 1996, (4): 36) in the reality.Four, impedance type hygrometer: be a kind of humidity measuring method of trying to achieve humidity according to the change in impedance value of moisture sensor, this method has response soon, and humidity hysteresis is little, measures the advantage of broad quantum; But measuring accuracy reaches the gauge head job insecurity inadequately in high temperature, high humidity environment, and is easily aging.Five, microwave moisture meter: it is a humidity of measuring air by the degree of absorption of air microwave radiation, though this method is measured broad quantum, and the strictness of instrument processing request, the cost height, and be not suitable for the fast measurement occasion of humidity variation.

In drying, Industrial Stoves and boiler smoke are analyzed, often relate to the problems of measurement of high temperature air humidity.And present existing various air humidity measuring methods and instrument, its measuring accuracy generally is that the measuring accuracy with relative humidity is an index, it is few to be applicable to that the hot environment air humidity is measured, and also unsatisfactory at aspects such as its measuring accuracy and instrument prices.Therefore, the feasible high-acruracy survey requirement of adopting conventional at present measuring method and instrument to be difficult to satisfy high temperature air humidity.Though have the temperature and humidity measurement instrument of high temperature range at present, can reach ± 1%RH in measuring accuracy as the multi-functional humiture transmitter of the EE29/EE31 of Pride company through its relative humidity after the special demarcation, but for high temperature air, as dry-bulb temperature is 140 ℃, relative humidity is 7% o'clock, the water capacity of air is 206.99g/kg, the absolute error of using this its water capacity of instrument measurement can reach ± 35g/kg～± 40g/kg, relative error is 15%～20%, and so big measuring error is difficult to accept.During particularly the drying experiment under laboratory high temperature, big air quantity operating mode was measured, the relative humidity measurement precision of ± 1%RH may cause full of prunes experimental result.Therefore, measure occasion, need a kind of new measurement means and instrument urgently, measurand is carried out high-precision measurement for some special hot environment air humiditys.

Summary of the invention

At the deficiency and the defective of existing air humidity measuring method and instrument existence, purpose of the present invention and task provide a kind of high temperature air moisture measurement new method, promptly adopt hot and cold mixed wind mode to measure the method for high temperature air humidity.This method not only can solve the not enough problem of conventional temperature and humidity measurement instrument measurement range and precision, and has that measuring method is simple, precision is high, the advantage that cost is low.

Purpose of the present invention and task are to realize by following technical solution:

A kind of high temperature air humidity measuring method is characterized in that this method adopts hot and cold mixed wind mode to measure, and its measuring process is as follows:

1) inlet at high temperature air is provided with temperature sensor, at Cryogenic air inlet and mixed wind exit dried, wet bulb temperature sensor is set respectively, temperature according to tested high temperature air, regulate the open degree of low temperature and high temperature air-valve, control the mixed wind ratio of hot and cold wind, its mixed air themperature is reached in the hygrometric range ability of dried, wet bulb temperature sensor;

2) utilize the dry-bulb temperature t of the tested high temperature air of temperature sensor measurement _g, dried, the wet-bulb temperature t of Cryogenic air _n, t _NsAnd dried, the wet-bulb temperature t of mixing back air _m, t _Ms

3) by step 2) the Cryogenic air of surveying and mix the doing of wind, wet-bulb temperature, calculate the absolute moisture content and the heat enthalpy value d of Cryogenic air and mixed wind according to soft air thermodynamic properties relational expression _n, i _nAnd d _m, i _m

4) by the thermodynamics energy balance and the mass balance relation of mixing the wind process, utilize step 2) the dry-bulb temperature t of institute's pyrometry air _gAnd the Cryogenic air that step 3) is calculated reaches absolute moisture content and the heat enthalpy value d that mixes wind _n, i _nWith d _m, i _m, the mixed wind that calculates the hot and cold wind under this measurement state compares r;

According to thermodynamic (al) heat, wet equilibrium relation, set up the heat balance and wet amount balanced relationship of hot and cold air mixed process:

G _g·i _g+G _n·i _n＝G _m·i _m (1)

G _g·d _g+G _n·d _n＝G _m·d _m (2)

G _m＝G _g+G _n (3)

And the mixed wind ratio that defines hot and cold wind is:

$r=\frac{G_n}{G_g}---\left(4\right)$

So can get by formula (1), formula (2), formula (3) and formula (4):

d _g＝(1+r)·d _m-r·d _n (5)

i _g＝(1+r)·i _m-r·i _n (6)

And the heat content of high temperature soft air can be expressed as:

i _g＝1.01t _g+0.001d _g·(2501+1.84t _g) (7)

＝a+b·d _g

The mixed wind ratio that can be got hot and cold air by formula (5)～formula (7) is:

$r=\frac{i_m-b\·d_m-a}{b\·(d_m-d_n)-(i_m-i_n)}---\left(8\right)$

In formula (1)～(8), the meaning of each physical quantity is:

G _g, G _n, G _m-high temperature air, Cryogenic air and the mass rate of mixing the back air

The mixed wind ratio of the hot and cold air of r-, r=G _n/ G _g

t _gThe dry-bulb temperature of-tested high temperature air

d _gThe absolute moisture content of-tested high temperature air, d _g=d _g(t _g, t _n, t _Ns, t _m, t _Ms)

d _nThe absolute moisture content of-Cryogenic air, d _n=d _n(t _n, t _Ns)

d _m-the absolute moisture content of air after mixing, d _m=d _m(t _m, t _Ms)

i _gThe heat enthalpy value of-tested high temperature air, i _g=i _g(t _g, d _g)

i _nThe heat enthalpy value of-Cryogenic air, i _n=i _n(t _n, t _Ns)

i _m-the heat enthalpy value of air after mixing, i _m=i _m(t _m, t _Ms)

A, b-constant coefficient, a=1.01t _g, b=2.501+0.00184t _g

t _n, t _NsDried, the wet-bulb temperature of-Cryogenic air

t _m, t _MsDried, the wet-bulb temperature of-mixed wind

5) the mixed wind that calculates by step 4) than r and step 3) gained Cryogenic air, mix the absolute moisture content and the heat enthalpy value d of wind _n, i _nWith d _m, i _m, calculate the absolute moisture content d of tested high temperature air _g

The absolute moisture content that formula (8) substitution formula (5) can be got high temperature air is:

$d_g=\frac{(i_n-a)\·d_m-(i_m-a)\·d_n}{b\·(d_m-d_n)-(i_m-i_n)}---\left(9\right)$

6) by step 2) the dry-bulb temperature t of the tested air of surveying _gAnd the absolute moisture content d of the tested air of step 5) gained _g, calculate wet-bulb temperature, relative humidity, dewpoint temperature and the enthalpy of tested high temperature air.

The invention is characterized in that control mixes the temperature of back air in the measurement range ability of conventional humiture instrument by regulating the mixed wind ratio of high temperature and Cryogenic air.Inlet at high temperature air is provided with temperature point, to measure the dry-bulb temperature of high temperature air; Reach mixed wind exit at the Cryogenic air inlet dried, wet bulb temperature sensor is set respectively, reach dried, the wet-bulb temperature that mixes wind to measure Cryogenic air.By measuring above-mentioned 5 temperature parameters, just can calculate each state parameter of tested high temperature air by thermodynamic relation, thereby realize adopting the measurement of conventional instrument high temperature air humidity.

The present invention compared with prior art has the following advantages and the high-lighting effect: 1. the inventive method adopts the measurement of conventional instrument realization to tested high temperature air humidity, has greatly reduced the cost of measurement instrument.2. the present invention only needs need not directly to measure the mixed wind ratio of the two according to mixing the blending ratio that the wind-warm syndrome degree is regulated hot and cold wind, and the simplified measurement process has reduced to produce the measurement links of error; 3. this method only relates to the dry-bulb temperature, Cryogenic air of tested high temperature air and mixes the measurement of the doing of wind, wet-bulb temperature, and measuring method is simple, is easy to realize; Under high temperature low humidity measurement environment, has the high advantage of measuring accuracy.4. since this method be by regulate mix wind than and by do, the measurement of wet-bulb temperature realizes the measurement to tested high temperature air humidity, so the inventive method only is subjected to the restriction of high temperature side temperature sensor measurement range theoretically; 5. the inventive method can realize the measurement of tested other each state parameter of high temperature air.

Description of drawings

Fig. 1 represents to adopt hot and cold mixed wind method to measure the schematic diagram of high temperature air humidity.

Fig. 2 represents the i-d figure of hot and cold air mixed process.

The title of each parts and each curve is respectively among the figure:

1-high temperature air channel; 2-high temperature air-valve; The 3-temperature sensor; The 4-blower fan; The 5-cryogenic wind-tunnel; 6-low temperature air-valve; 7-Cryogenic air side is done, wet bulb temperature sensor; The 8-mixing chamber; 9-mixes the air channel; The mixed wind side of 10-is done, wet bulb temperature sensor; G-high temperature air state point; N-Cryogenic air state point; M-mixes the wind state point; C ₁-hot and cold wind mixes the wind graph; C ₂-100% relative humidity line.

Embodiment

Below in conjunction with drawings and Examples principle of the present invention and implementation process are further described.

The method of hot and cold mixed wind realizes the measurement of high temperature air humidity

Embodiment:

1 arrange each temperature point with reference to the accompanying drawings, survey the dry-bulb temperature that tested high temperature air state point G of a certain moment orders and be: t _g=140 ℃, dried, wet-bulb temperature that low ambient temperature air condition N is ordered are: t _n=20 ℃, t _Ns=15.76 ℃.According to surveying the dry-bulb temperature t that G is ordered _gThe open degree of regulating high temperature air-valve 2 and low temperature air-valve 6 makes the air mixed of state point G and N to the M point of doing, wet bulb temperature sensor hygrometric range ability is interior.Dried, the wet-bulb temperature that record admixture point M point air are respectively: t _m=62 ℃, t _Ms=43.31 ℃.Each is done, the measuring accuracy of wet bulb temperature sensor is: ± 0.1 ℃, ignore the thermal loss of each pipeline, and each wet-bulb temperature measuring point place wind speed is 2.5m/s.

According to each temperature value of measuring, method and the step of calculating the humidity of tested high temperature air and each state parameter are as follows:

1., concern that according to the soft air thermodynamic properties saturation vapor pressure of soft air is:

$P_{\mathrm{qb}}=98066.5\exp [0.0326889-7.235425(\frac{{10}^3}{273.16+t}-\frac{{10}^3}{373.16})+8.2\ln \left(\frac{373.16}{273.16+t}\right)-0.00571133(100-t)]---\left(10\right)$

The partial pressure of water vapor is in the soft air:

P _q＝P _qbs-A(t-t _s)B (11)

The absolute moisture content and the heat enthalpy value of soft air are respectively:

$d=622\frac{P_q}{B-P_q}---\left(12\right)$

i＝1.01t+0.001d(2501+1.84t) (13)

In formula (10)～formula (13), the meaning of each physical quantity is as follows:

P _QbsThe saturation vapor pressure of-corresponding wet-bulb temperature calculates by formula (10)

P _qThe partial pressure of water vapor in the-soft air

The dry-bulb temperature of the corresponding measuring point of t-, t=t _n, t _m

t _sThe wet-bulb temperature of-corresponding measuring point, t _s=t _Ns, t _Ms

The coefficient that A-is relevant with wind speed can be calculated as:

$A=(593.1+\frac{135.1}{\sqrt{u}}+\frac{48}{u})\×{10}^{-6}---\left(14\right)$

The u-wind speed, u 〉=2.5m/s

The local atmospheric pressure of B-

The absolute moisture content of the corresponding measuring point of d-, d=d _n, d _m

The heat enthalpy value of the corresponding measuring point of i-, i=i _n, i _m

The absolute moisture content and the heat enthalpy value that are calculated Cryogenic air and mixed wind by formula (10)～formula (13) are respectively:

d _n＝9.471g/kg，i _n＝44.2355kJ/kg；

d _m＝51.107g/kg，i _m＝196.2689kJ/kg

2., calculate a, the b value is respectively by formula (7):

a＝1.01t _g＝1.01×140＝141.4

b＝2.501+0.00184t _g＝2.501+0.00184×140＝2.7586

3., the mixed wind that calculates hot and cold wind by formula (8) is than r:

$r=\frac{196.2689-2.7586\×51.107-141.4}{2.7586\×(51.107-9.471)-(196.2689-44.2355)}=2.3164$

4., calculate the absolute moisture content d of tested high temperature air by formula (9) _g:

$d_g=\frac{(44.2355-141.4)\×51.107-(196.2689-141.4)\×9.471}{2.7586\×(51.107-9.471)-(196.2689-44.2355)}=147.552g/\mathrm{kg}$

5., according to the propagation of error theory, for Cryogenic air and mix the wind state point, the resultant error of its water capacity and heat enthalpy value can be expressed as with relation between dried, the wet bulb temperature sensor measuring accuracy:

$\mathrm{\δd}=\sqrt{{(\frac{\∂d}{{\∂P}_q}\·\frac{\∂P_q}{\∂t})}^2\·{\mathrm{\δ}}^{2}t+{(\frac{\∂d}{{\∂P}_q}\·\frac{{\∂P}_q}{\∂t_s})}^2\·{\mathrm{\δ}}^2{t}_s}---\left(15\right)$

$\mathrm{\&delta;i}=\sqrt{{\left(\frac{\&PartialD;i}{\&PartialD;t}\right)}^2\&CenterDot;{\mathrm{\&delta;<figure-callout\; id="2"\; label="t"\; filenames="C20051001116900111.png"\; state="\{\{state\}\}">t</figure-callout>}}^2+{\left(\frac{\&PartialD;i}{\&PartialD;d}\right)}^2\&CenterDot;{\mathrm{\&delta;d}}^2}---\left(16\right)$

For tested high temperature air, on the basis of formula (9),, the resultant error of its water capacity and relative humidity measurement value can be expressed as following form by the propagation of error theory:

$\mathrm{\&delta;}{d}_g=\sqrt{{\left(\frac{{\&PartialD;d}_g}{{\&PartialD;i}_n}\right)}^2\&CenterDot;{\mathrm{\&delta;}}^2{i}_n+{\left(\frac{{\&PartialD;d}_g}{{\&PartialD;i}_m}\right)}^2\&CenterDot;{\mathrm{\&delta;}}^2{i}_m+{\left(\frac{{\&PartialD;d}_g}{{\&PartialD;d}_m}\right)}^2\&CenterDot;{\mathrm{\&delta;}}^2{d}_m+{\left(\frac{{\&PartialD;d}_g}{{\&PartialD;d}_n}\right)}^2\&CenterDot;{\mathrm{\&delta;}}^2{d}_n+{\left(\frac{{\&PartialD;d}_g}{\&PartialD;a}\right)}^2\&CenterDot;{\mathrm{\&delta;}}^{2}a+{\left(\frac{{\&PartialD;d}_g}{\&PartialD;b}\right)}^2\&CenterDot;{\mathrm{\&delta;}}^{2}b}---\left(17\right)$

In formula (15)～formula (18), the meaning of each physical quantity is as follows:

The measuring accuracy of the corresponding measuring point dry-bulb temperature sensor of δ t-, δ t=δ t _n, δ _Tm

δ t _sThe measuring accuracy of-corresponding measuring point wet bulb temperature sensor, δ _t=δ t _Ns, δ t _Ms

The resultant error of the corresponding measuring point water capacity of δ d-, δ d=δ d _n, δ d _m

The resultant error of the corresponding measuring point heat enthalpy value of δ i-, δ i=δ i _n, δ i _m

δ t _g-high temperature air dry-bulb temperature sensor measuring accuracy

δ d _gThe resultant error of-tested high temperature air water capacity measured value

The resultant error of-tested high temperature air relative humidity measurement value

δ a, δ b-t _gMeasuring accuracy is to a, the influence of b value, δ a=1.01 δ t _g, δ b=0.00184 δ t _g

The resultant error of being calculated Cryogenic air and mixed wind state point water capacity and heat enthalpy value by formula (15) and formula (16) is respectively:

δd _n＝0.1229g/kg，δi _n＝0.1028J/kg；

δd _m＝0.3788g/kg，δi _m＝0.1183J/kg

According to the propagation of error theory, can be under this to measure operating mode by formula (17) and formula (18), the absolute moisture content of tested high temperature air and relative humidity measurement error are respectively:

δd _g＝±5.1415g/kg

6., by the dry-bulb temperature t that surveys high temperature air _gAnd the absolute moisture content d that calculates 4. _g, utilize thermodynamic relation can determine that other each state parameter of tested high temperature air is respectively:

Relative humidity:

Dewpoint temperature: t _l=59.44 ℃;

Wet-bulb temperature: t _s=63.34 ℃;

Enthalpy: i _g=547.59kJ/kg

Under this embodiment condition, adopt existing high temperature air humidity measuring instrument (the multi-functional humiture transmitter of the EE29/EE31 of Pride company), measuring range is 40 ℃～180 ℃, the relative humidity measurement precision is ± 1%RH after special demarcation, this moment water capacity measuring error be-32.6g/kg～+ 35.6g/kg; And employing the inventive method, the measuring error of water capacity is ± 5.1g/kg that the measuring error of relative humidity is ± 0.154%.Therefore, can find: for the measurement of high temperature air humidity, adopt the inventive method can greatly improve the precision of measurement result, reduce measuring error by the comparative result of embodiment; Also reduced simultaneously the cost of measurement instrument, made measuring method more economical, effective.

Claims (1)

1. a high temperature air humidity measuring method is characterized in that this method adopts hot and cold mixed wind mode to measure, and its measuring process is as follows:

1) inlet at high temperature air is provided with temperature sensor, at Cryogenic air inlet and mixed wind exit dried, wet bulb temperature sensor is set respectively, temperature according to tested high temperature air, regulate the open degree of low temperature and high temperature air-valve, control the mixed wind ratio of hot and cold wind, its mixed air themperature is reached in the hygrometric range ability of dried, wet bulb temperature sensor;

2) utilize the dry-bulb temperature t of the tested high temperature air of temperature sensor measurement _g, dried, the wet-bulb temperature t of Cryogenic air _n, t _NsAnd dried, the wet-bulb temperature t of mixing back air _m, t _Ms

3) by step 2) the Cryogenic air of surveying and mix the doing of wind, wet-bulb temperature, calculate the absolute moisture content and the heat enthalpy value d of Cryogenic air and mixed wind according to soft air thermodynamic properties relational expression _n, i _nAnd d _m, i _m

4) by the thermodynamics energy balance and the mass balance relation of mixing the wind process, utilize step 2) the dry-bulb temperature t of institute's pyrometry air _gAnd the Cryogenic air that step 3) is calculated reaches absolute moisture content and the heat enthalpy value d that mixes wind _n, i _nWith d _m, i _m, the mixed wind that calculates the hot and cold wind under this measurement state compares r;

According to thermodynamic (al) heat, wet equilibrium relation, set up the heat balance and wet amount balanced relationship of hot and cold air mixed process:

G _g·i _g+G _n·i _n＝G _m·i _m (1)

G _g·d _g+G _n·d _n＝G _m·d _m (2)

G _m＝G _g+G _n (3)

And the mixed wind ratio that defines hot and cold wind is:

$r=\frac{G_n}{G_g}---\left(4\right)$

So can get by formula (1), formula (2), formula (3) and formula (4):

d _g＝(1+r)·d _m-r·d _n (5)

i _g＝(1+r)·i _m-r·i _n (6)

And the heat content of high temperature soft air can be expressed as:

i _g＝1.01t _g+0.001d _g·(2501+1.84t _g) (7)

＝a+b·d _g

The mixed wind ratio that can be got hot and cold air by formula (5)～formula (7) is:

$r=\frac{i_m-b\&CenterDot;d_m-a}{b\&CenterDot;(d_m-d_n)-(i_m-i_n)}---\left(8\right)$

In formula (1)～(8), the meaning of each physical quantity is:

G _g, G _n, G _m-high temperature air, Cryogenic air and the mass rate of mixing the back air

The mixed wind ratio of the hot and cold air of r-, r=G _n/ G _g

t _gThe dry-bulb temperature of-tested high temperature air

d _gThe absolute moisture content of-tested high temperature air, d _g=d _g(t _g, t _n, t _Ns, t _m, t _Ms)

d _nThe absolute moisture content of-Cryogenic air, d _n=d _n(t _n, t _Ns)

d _m-the absolute moisture content of air after mixing, d _m=d _m(t _m, t _Ms)

i _gThe heat enthalpy value of-tested high temperature air, i _g=i _g(t _g, d _g)

i _nThe heat enthalpy value of-Cryogenic air, i _n=i _n(t _n, t _Ns)

i _m-the heat enthalpy value of air after mixing, i _m=i _m(t _m, t _Ms)

A, b-constant coefficient, a=1.01t _g, b=2.501+0.00184t _g

t _n, t _NsDried, the wet-bulb temperature of-Cryogenic air

t _m, t _MsDried, the wet-bulb temperature of-mixed wind

5) the mixed wind that calculates by step 4) than r and step 3) gained Cryogenic air, mix the absolute moisture content and the heat enthalpy value d of wind _n, i _nWith d _m, i _m, calculate the absolute moisture content d of tested high temperature air _g

The absolute moisture content that formula (8) substitution formula (5) can be got high temperature air is:

$d_g=\frac{(i_n-a)\&CenterDot;d_m-(i_m-a)\&CenterDot;d_n}{b\&CenterDot;(d_m-d_n)-(i_m-i_n)}---\left(9\right)$

6) by step 2) the dry-bulb temperature t of the tested air of surveying _gAnd the absolute moisture content d of the tested air of step 5) gained _g, calculate wet-bulb temperature, relative humidity, dewpoint temperature and the enthalpy of tested high temperature air.

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