DD203141A1 - METHOD FOR DETERMINING THE AMOUNT OF A PARTIAL FLOW OF A STROEMENING MEDIUM - Google Patents

Abstract

The invention relates to a method for determining the quantity of the partial flow of a flowing medium from the results of a quantitative measurement of the total flow. The aim of the invention is to make a clear determination of the auszen entering into the system cold air quantities in a given pipeline or duct system in which there is a Kurzschluszverbindung from the pressure-side Heiszluftkanal the blower to the suction side. The invention has for its object to determine in the given pipeline or duct system from the mesztechnisch immediately before Luefter determined total air flow (mixed air flow), the size of the auszenzen sucked partial air flow over heat balance. According to the invention, this is achieved by measuring the temperatures of the partial currents and of the total current and generating a signal according to the Therm formula by way of a first computing element, which measures the amount of the total current in a known manner and generates a signal according to the Therm formula via a second computing element and that both signals are multiplied by a third arithmetic means, such that the output of the third arithmetic means is proportional to the amount of the sub-stream.

Description

235U0 0

(Title of the invention

Method for determining the amount of a partial flow of a flowing medium

Field of application of the invention

The invention "relates to a method for determining the amount of the partial flow of a flowing medium from the amount of the total flow of the flowing medium.

Such a task, z. B * in air systems of steam generators, if- a cold air and a hot air partial flow is mixed and the amount of Ealtlüftstromes is to be determined, which can not be measured directly.

Characteristic of the known technical solutions

In piping and sewer systems, it is often necessary to measure the amount of liquid or gas flowing through it in order to determine the mass flow (kg / h) or volume flow m m-yhjzu.

However, there are known pipeline and duct systems, which are partially, by cold air, partly by hot air, partly by mixed air flows through »Z. B. air is sucked through two possible intake air from the atmosphere. This air is forced through the fan by an air preheater. After the air preheater, a partial flow der'erhitzten air is diverted

W I

and about one with one. The task "is to measure the amount of cold air entering the system from the outside, but it is not possible to measure the amount of cold air in the piping system before the hot recirculation air" until the mixing point two possible suction paths no unbalanced speed spr il up to the point of union with the hot air is present.

Immediately before entering the blower, there is the opportunity to carry out a quantity measurement. The Binfluß of. Different intake from the atmosphere has subsided to the suction nozzle in front of the blower, but at this point only a faulty measurement is possible ^ a "with open bypass control constantly a certain amount of hot air flowing through the bypass duct in the suction line , measured with «

Also known is a calorimetric method in which a flowing medium - usually via an electrical resistance - a precisely defined amount of heat is supplied and in which the flow rate of the medium is determined by measuring the temperature before and after the heat spreader.

Object of the invention

The aim of the invention is to make a clear determination of the entering from outside into the system cold air quantities in the given pipeline or duct system in which there is a short circuit connection from the pressure side hot air duct of the fan to the suction side.

Explanation of the essence of the invention

The invention is based on the object, in the given pipeline or duct system from the total amount of air detected immediately before the fan (mixed

-J-

L 3 Ό Ι 4 UU

Ventilation volume) to determine the size of the sucked in from the outside partial air volume on Wänaebalanzen.

According to the invention, this is achieved by measuring the temperatures of the filar streams and of the total current and by means of a first computer a signal according to the Therm

is generated, that measured in a known manner, the amount of the total current and a second computing element, a signal after the! Therm

is generated and that both signals are multiplied by a third Hechenglied, such that the output signal of the third-arithmetic unit is proportional to the amount of the partial stream ·

Depending on the structure of the measuring chain and the computer, the Therm can also be formed in a single calculation

embodiment

In one embodiment, the invention is explained in detail.

The drawing shows schematically simplified fragmentary the air system of a steam generator.

via one of the suction elements 1; 2, cold air is sucked in from the outside (from the outside or from the boiler house). The cold

loft 17 flows to mixing point 3, at which hot air 18 is supplied. The mixed air 19 is supplied to the fan 5 via the Mengenmeßstelle 4. Here, the total amount of air (mixed air = cold air + hot air) is measured. The mixed air 19 is conveyed into the air preheater 6 and heated there. The main stream of the hot air 18 is conveyed to the consumers (for example burner of the steam generator). "The partial stream 23 is diverted at the integration 7 and conveyed via the control element 8 to the mixing point 3. Before the mixing point 3 the temperature measuring point 9 is for the cold air 17 arranged by which the temperature tg- ^ is measured *

Before or after the fan 5 is the temperature measuring 10; 11 is arranged for the mixed air 19, by which the temperature t 1 is measured; compartment integration 7 is one of the temperature measuring points 12; 13 arranged for the hot air, through which the temperature trrr is measured '· The temperature measuring 9 »10; 11; 12; 13 are connected to the calculating member 14 that the signal 20 after the Therm

_v ¹¹ HL "* ¹¹ KL /

generated.

The Mengenmeßstelle is connected to the computing device 15 that the signal 21 after the Therm

generated.

The signals 20; 21 are connected to the input of the computing element 16 and are multiplied in the six-member 16. The output signal 22 of the computing element 16 is proportional to the amount of the sought sub-stream.

The thermal baths are determined according to the mixing rule on the basis of the heat balances, which reads as follows: The heat balance is:

^m! HL * ° PHL * ¹³ HL ^{+ m} *

^C PEL * ¹ XL = ^{m #} HL '' ⁰

HL * ° PHL * ¹³ HL ^{+ m} KL ^VC PEL * ¹ XL = ^m HL ' ⁰ PmL * If neglecting the differences of Cpm, ⁽ ^ vkt, ^{s 0} PmL

_ ♦ _. HL m ΤΤ-Γ = m, - KL ML t

m * = mass flow rate [kg / aJ

c = specific heat [kJ / kg grdj

t = temperature L ⁰ CJ

Indiees5

HL = hot air

KL = cold air

IL a mixed air

In the Hegel applies to the transmitter before fans

tj2. __ ·, ν P tsl f λ \

(273 + W)

*

Hit Relationships (2) and (4) results for the searched m ^>

just - 73 pounds

^t HL " ^t ML " - ¹³ KL

k = calibration constant / = density [kg / m ³ ] Y = Yolumen flow

[kp / m ² ]

Index:

0 = in Uormzüstanä.

In Thermy ^ PjT-T /, k is a constant that usually passes through

k calibration is obtained. The formation of the root for PrHff ^w ^ "in the case of commercially available transmitters is generally carried out by means of a reducer» To conclude from the measurement result before the fan on the cold air quantity.

Ben to be able to, are the temperatures t ^, * kl ^ ^ m ₁ ^to and by means of a Recliengliedes, z. BV microcomputer, as follows to combine!

Rechengliedi

- * hl \

^a KL /

This arithmetic unit is then multiplied by the 5! Herm k *.

Claims (1)

1 * t Erf indungsanspruc h 1. A method for determining the amount of a Teilstroin.es a flowing medium aas the amount of the total flow of the flowing medium, wherein the partial streams have different temperatures, characterized in that the temperatures of the partial streams and the total current measured and a first Hechenglied a signal after the therm is generated, that measured in a known manner, the amount of the total current and a second computing element a
Signal after the therm is generated and that both signals are multiplied by a third quadrant, such that the output signal of the third computing element is proportional to the amount of the partial stream. 2v method according to item 1, characterized in that the
Temperatures of the partial flows and of the total flow and a characteristic pressure difference (P ^ ff) of ^the total current in a known manner for determining the amount of the total current are measured and one or more six-membered signal according to the Therm is produced.
For this 1 sheet drawing