Thermal measuring and testing – Calorimetry – Gain or loss of heat by heat utilizing load in path of heat...
Patent
1982-01-26
1984-04-03
Goldstein, Herbert
Thermal measuring and testing
Calorimetry
Gain or loss of heat by heat utilizing load in path of heat...
G01K 1708
Patent
active
044405073
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns a procedure for measuring thermal energy transported with the aid of fluid flow. The procedure of the invention is appropriate for measurement both of the increase and decrease of the heat contents in the heat-transporting fluid. The commonest area of application of the procedure is a commercial area heating distribution network, specifically for each house or for each area. The fluid transporting thermal energy may be any uniformly flowing fluid as regards its state of aggregation and its chemical composition, its most important characteristic being a high specific heat value.
Present-day heat quantity or thermal energy measurement techniques are based on separate measurement of a temperature differential .DELTA.T=T.sub.1 -T.sub.2 and separate measurement of a volumetric flow V, the rate of change of thermal energy content then being: density of the fluid and specific heat is completely omitted nowadays, implying that no provision is made for their variations. If steps are taken to employ as thermal energy-transporting fluid, water which has been improved with additive substances, it is well conceivable that .rho.C may not always be as constant as is the case with pure water.
Of the various quantities to measured, V is substantially less accurate than .DELTA.T; if endeavours are made to improve the measuring accuracy of V, this leads to very expensive meters, such as e.g. the inductive (magnetic) flow meter, which has a metering error amounting to (.+-.0.5% of the reading)+(.+-.0.5% of full scale deflection).
The limitations imposed by area heating technology on the developing of the method of measurement--to mention a few of them--are:
the meter must not cause any significant increase in demand of pumping work; the upper limit for the pressure drop is quite generally 0.1 bar;
the power consumption of the meter should be minimized, and it must not exceed 0.1% of the thermal energy rate that is being measured;
the price at which the meter sells should be concordant with the savings regarding errors in the charging, owing to heightened accuracy of measurement.
SUMMARY OF THE INVENTION
The object of the invention is to achieve an improvement of previously known methods for measuring thermal energy transported by fluid flow. The more detailed object of the invention is to teach a procedure which is independent of the fluid's density and specific heat. Still one further object of the invention is to provide a procedure wherein the flow rate need not be measured at all. The rest of the objects of the invention, and the advantages gained with its aid, with become apparent in the disclosure of the invention.
The objects of the invention are attained by a procedure which is mainly characterized in that there is provided in parallel across the consumption unit (where the thermal energy is withdrawn from the fluid passing through the incoming line), a fluid by-pass flow through a by-pass line; that into said fluid by-pass flow is introduced or therefrom withdrawn thermal energy at a given rate; and that in said incoming line, in said return line and in said by-pass line respectively are measured the temperatures of the fluid flowing through said incoming line, the fluid flowing through said return line, and the fluid by-pass flow flowing through said by-pass line respectively, whereby the thermal energy transported with the aid of the fluid flow is measurable by the exclusive aid of the rate at which energy is introduced into the said fluid by-pass flow and of the said temperature measurements.
A number of significant advantages are gained by using the procedure of the invention.
The procedure of the invention contains in actual fact no measurement of flow rate at all, in the conventional sense, instead of which one permits a minor fluid short-circuit flow past the change-of-energy object under measurement (a heat exchanger for instance). In the procedure of the invention, one measures the rate at which the fluid's heat content changes in the object, mer
REFERENCES:
patent: 3167957 (1965-02-01), Ziviani
patent: 4362404 (1982-12-01), Armstrong
Hirsimaki Olavi
Karras Matti R.
Goldstein Herbert
Valmet Oy
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