Year: 1909
Type: article
Abstract: The meter described by Professor Thomas should prove a valuable addition to the instruments used in gas engine and other testing.The possibilities of error in the indications of such an instrument must be fully examined.2 This meter is fundamentally an instrument for determining the weight of gas or vapor flowing through it and is made to record volumes.It is obvious that these volumes cannot be those actually flowing but must be the volumes reduced to some standard conditions of temperature and pressure.The author has not mentioned this matter in his paper, but it is of considerable importance.A variation of 5 deg.fahr. in temperature, or of 0.3 lb. in pressure, under ordinary atmospheric conditions, would result in an error of 1 per cent in the indications of the instrument if it were assumed to record actual volumes flowing.The calibration of the instrument by passing through it a known volume of a gas at known pressure and temperature, can easily be reduced to a calibration under standard pressure and temperature conditions.3 In Par.16 the author refers to the effect of water vapor carried in with the gas.He states that, in consequence of the small rise of temperature, the water vapor does not experience a change of state, and that, consequently, the latent heat of vaporization does not enter into consideration.It is obvious that he is considering here the case of a gas which not only is saturated with water vapor, but also is bringing with it minute particles of water in suspension.Under these conditions-and they are conditions which may easily obtain with blast-furnace gas which has just passed through the washersthe indications of the instrument will be rendered completely useless.4 If the gas should enter at a temperature of 70 cleg.fahr. it would contain 0.001148 lb. of water vapor.After passing through the meter with a rise of temperature of 5 cleg, the same weight of gas could contain 0.001198 lb. of vapor; that is, there would occur a vaporization of 0.00005 lb. of moisture for every cubic foot of gas passing through the meter.The latent heat of vaporization at these temperatures is about 1050 B.t.u., or 0.0525 B.t.u. will be used in converting the water into vapor.As the total heat required for raising one cubic foot of the gas 5 deg.fahr. is only about 0.1 B.t.u., we have here, obviously, the possibility of an error of the magnitude of 20 or 25 per cent in the indications of the instrument in the
DOI: 10.1115/1.4060228
Authors: L. S. Marks, W. D. Ennis, Edwin D. Dreyfus, A. R. Dodge, Carl C. Thomas
Language: English
Subfield: Instrumentation
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W4390044481