DE2235853B2 - Method and device for determining the moisture content of gases - Google Patents

Description

The invention relates to a method for determining water outlet temperature sensors are arranged, the moisture content of gases, in particular for high measured values thereof in a computing circuit according to FIG Gas temperatures and gas humidities can be linked by deposition 40 heat balance equation, of the water from a continuous measuring gas flow It is advisable to install a heater at the gas inlet. and determining the occurring, viewed on one.

Amount of heat transferred by the measurement The invention in particular provides the following

the temperature of that body. It also relates to the advantages achieved: The measurement is carried out continuously,

Invention a device for carrying out this 45 and the measurement result can continuously directly - z. Am Procedure. g / kg - displayed on an instrument The moisture content of the air has z. B. can be used in the dry or as a control signal. That

nungstechnik meaning. For optimal guidance of the measuring process is absolute and does not require any calibration.

Drying processes, it is desirable to measure the temperature.

temperature and humidity of the drying agent. Since only small gas flows and cooling

to monitor continuously. The application of direct services is required, there are short

Heating in dryers has led to exhaust air consultation times.

temperatures above 100 ^c C and humidity of the exhaust air. The invention is described below with reference to the

up to 1000 g / kg can be driven. With the direct drawing in which an embodiment is shown

heating is often associated with the presence of 55, explained in more detail.

SO ₃ steaming. Measurement methods that are directly or indirectly F i g. 1 shows the overall arrangement sixmatically;

based on the measurement of the partial vapor pressure - F i g. 2 shows the block diagram of the electronic

z. B. dew point measurement or psychrometry - are arithmetic circuit.

therefore not usable. The measuring gas stream to be examined passes over

In the book »Measuring and regulating in the chemical 60 a feed line 1 in a continuously working Technology «von Hengstenberg - Sturm - Countercurrent Cooler3. Temperature sensors in one W i η k 1 e r, Springer-Verlag, 2nd edition 1964, is arranged on nozzle 2, measure the inlet temperature P. 662 in Fig. 39 and the associated text already rature of the measuring gas flow. This is in the cooler 3

«Is described in the device in which a test gas flow is guided downwards in a spiral-like manner via a pipe coil

a dry substance is passed and thereby its 65 and leaves this through a line 5. In one

Releases moisture to the dry substance. The here- nozzle 4 is the gas outlet temperature measured,

when absorption heat occurs is a measure for the flow of a KUhI-

Gas humidity. The temperature increase is measured water flow, which is via a line 6 and a measuring

nozzle 7 enters the radiator 3 The cooling water leaves the cooler 3 via a measuring port 8 and a line 9 through which it flows into the open air

The cooled gas and the condensate pass via line 5 into a cooling water storage tank 10. There the condensate is separated from the gas flow. The condensate-free air is via a line 11 of sucked in a pump 12 and pressed into a line 13. This leads to pressure equalization back to Tapping point. The cooling water reaches the storage tank 10 via a valve 14 Cooling water is sucked in via a line 13 and conveyed into the cooler 3 by a pump 16. The two Pumps 12 and 16 are driven by a motor 17 via a common shaft. This is the ratio of the conveyed volume flows regardless of the speed. Cooler 3 and temperature measuring points sit in an insulating housing.

The measured value is obtained in an analog computer 18 from the measured temperature values in the nozzles 2, 4, 7 and 8 The balance equation of the heat exchanger is formed to generate the measured value

mw cw (& WA - & wb) + Qv

= niLTR {CPL (& LB - & La) + r ₀ {XLE - XLA)

+ CPD {XLE ■ & LE - XLA · 1

by the approximation
(A + B + C) -

1 + 0.747 -10- ³ oils

- XLB 2

replaced.
It is

A ■ - = (& WA - & wb) [- · k · 1.675 · 10 " ³ \ \ rriLO j

(1 + 6.2 · 10- »

B = (& LB - Ha) · 0.40 · 1Ü- ³ & LA, C = XLAS (1 + 0.747 · 1Ο- · 0ιμ).

Herein means

Drying air (= sample gas) -] reference-> Mass flow,

m _w water (== coolant) - J

Cw specific heat of the water, J j temperature of the water ( \ temperature of the drying air i \

Heat of evaporation of water (condensation heat),

> Moisture content of the drying air} '

Qv

at entry, J * { at exit,

Heat of evaporation of water (condensation heat),

at entry at exit,

Degree of saturation humidity at temperature & la (is simulated in the circuit by a diode function generator), heat loss to the area around the cooler. Qv is set proportional to mwCw ißwA - 0 »b).

The error of the approximation is carried out ⁰ C for the range 5 ° C <& _LA <5O and 50 ° C <& le <300 ⁰ C at most 2%. The specified equation (2) is executed by the analog computer 18, the circuit diagram of which is shown in FIG. 3 is shown. The air outlet temperature is measured three times and the air inlet temperature twice. Pt-100 measuring resistors are generally used for measurement. A Ni-100 resistance thermometer is used for multiplication by the factor in the summand Λ, which depends on & la. From equation A it can be seen that mw and / h & o need not be constant individually, but only their ratio. No calibration is necessary, just two settings. The first setting concerns the output level. For this purpose, a temperature difference in summand B has to be simulated. B indicates the conversion of sensible heat into latent heat.

The second setting concerns the adjustment of the apparatus constants

mw, _

For this purpose, the exchanger is operated with dry air, as high as possible, but at any temperature. Only sensible heat is exchanged. The summands A and B must compensate each other to 0. This condition is set.

The setting can be checked and repeated from time to time if necessary. This can be done in the Air inlet a heater 22 can be provided.

The cooling water flow can also be circulated. Then there are no water inlets and outlets necessary. The water is cooled by a suitable cooling unit. The formation of the measured value takes place in the same way as with an open cooling water flow.

The partial air flow can also be cooled directly by means of a Peltier cooler instead of cooling water take place. The cooling capacity is a measure of the change in enialpy in the air.

For this purpose 2 sheets of drawings

Claims (3)

against a comparison stateA From apparent patent claims: For reasons, the measurement can only be carried out intermittently, and only up to a gas temperature of 1. A method for determining the Feuchtegebaltes about 100 ⁰ C. Moreover, the heat of absorption depends from Gaoen, especially for high gas temperatures S of the respective assignment of the absorber off. The device, which is humidified by gas, has a measuring range from 0 to a continuous flow of measuring gas and 100 ppm of water in volume. Correct the amount of heat that occurs and is transferred to a body. In Fig. 40 on p. 663 of the above-mentioned book, a moisture meter is shown in which the temperature of this body, thereby sucked in, indicates the moist, hot gas in the Liebigkuhler that the measuring gas flow is also cooled. The water condensed out in the process is collected in two measuring vessels with the help of a continuously operating cooler, while the heat output exchanged with the remaining amount of gas measured by a gas meter cooler is cooled below the dew point. The device also only allows the temperature of the measuring current to be discounted and measurements taken. is measured after cooling and the object of the invention is to provide a Find out the moisture content from the heat balance equation of the type mentioned at the beginning, is averaged. in which the measurement is continuous, with little 2. Device for carrying out the procedure speaking time, at any gas temperature and in particular claim 1, characterized in that 20 ders can also be carried out with high gas humidity. As the measuring gas flow through a countercurrent flow, the task is then to develop a measuring device for the cooler (3) sucking pump (12) and a joint implementation of such a method, together with the pump (12) by a motor (17) according to According to the invention, the measuring gas flow is driven by a "coolant flow" provided by a continuously operating cooler under cooler (3) promoting pump (16), the dew point is cooled down, which goes out with the cooler and that in the gas inlet and gas outlet as well as in the exchanged Thermal output measured, the temperature of the cooling water inlet and cooling water outlet tem- measuring gas flow before and after the cooling down perature sensors (2, 4, 7, 8) are arranged, which measure and the moisture content is determined via the heat balance measured values in a computing circuit (18) according to equation. can be linked to the heat balance equation. 30 A suitable one to carry out the procedure 3. Device according to claim 2, characterized according to the invention, the device is characterized by a heater (22) at the gas inlet. indicates that a measuring gas flow through a Countercurrent cooler sucking pump and a motor driven jointly with the pump, 35 promoting a flow of coolant through the radiator Pump are provided and that in the gas inlet and gas outlet as well as in the cooling water inlet and cooling