File:Pacific service magazine (1918) (14783344135).jpg

Identifier: pacificservicema1019paci (find matches)
Title: Pacific service magazine
Year: 1912 (1910s)
Authors: Pacific Gas and Electric Company
Subjects: Pacific Gas and Electric Company Electric utilities Electrical engineering Public utilities
Publisher: San Francisco : Pacific Gas and Electric Company
Contributing Library: San Francisco Public Library
Digitizing Sponsor: San Francisco Public Library

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ay be dry,or what is known as saturatedsteam, that is, all the water hasbeen changed from water intosteam, or it may be superheatedby further adding heat units afterit has become saturated steam. Steam cannot be materially superheatedwhile it is in contact with the water inthe boiler, on account of the heat unitsforced into the saturated steam beingtransmitted to the water, raising thetemperature of the water and turning itinto saturated steam. In expanding a working substance suchas water and steam isothermally underconstant pressure and constant tempera-ture it is necessary to add heat to thesubstance; that is, in other words, to in-crease the volume of the substance, re-taining its pressure and temperature, itis necessary to add heat to it, as shownin Fig 8, which portrays a cylinder con-taining the working substance of waterand steam, a weighted piston that is freeto move up or down within the cylinder.Applying heat to the working substancewill cause the piston to rise, increasing
Text Appearing After Image:
Fig. 7 104 Pacific Service Magazine the volume of the working substance butnot increasing its pressure or temperature.In compressing steam isothermally un-der constant pressure and temperature itis necessary to extract heat from it. When expanding steam adiabaticallyyou reduce or lessen its pressure and tem-perature, as shown in Fig. 9, which showsa horizontal cylinder with a movablepiston. By filling the closed space in thecylinder with steam and drawing thepiston out towards the end of the cylinderthe pressure and temperature will bereduced as shown by the adiabatic lineof the diagram. In compressing steam adiabatically youincrease its pressure and temperature. I mention these two methods of expand-ing steam to make clear the differencebetween the generation ofsteam in the boiler and theextraction of the heat unitscontained in the steam indoing useful mechanicalwork, as in steam engines. In the boiler we expandthe working substanceisothermally, keeping itspressure and temperaturecon

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