THE JOULE-THOMSOX EFFECT IN SUPERHEATED STEAM : 

 I. EXPERIMENTAL STUDY OF HEAT-LEAKAGE. 



By H. M. Trueblood, 



Received, January 14, 1917. 



CONTEXTS. 



Page 



I. Introduction 734 



II. The throttling apparatus 735 



1. Axial flow apparatus 735 



2. Radial flow apparatus 738 



a. General remarks on the radial flow plug .... 738 



b. The V-type of radial flow plug-case 741 



c. The U-type of radial flow plug-case 742 



d. The straight-away type of radial flow plug case . . 743 

 III. Other apparatus 743 



1. Oil bath and secondary superheater 744 



2. Boiler, primary superheater and condenser 748 



3. Pressure-measuring apparatus 750 



4. Thermometers and the measurement of temperature . 754 



a. Description of thermometers 754 



b. Effect of conduction of heat down the stem of the 



thermometer 755 



c. Radiation effects 757 



d. Effect of heat conduction along the thermometer 



leads and of unequal temperature distribution in 



these leads 758 



e. Contact resistances . 759 



/. Variations in lead-resistance 759 



g. Calibration of differential thermometers .... 760 



h. Calibration of individual thermometers .... 766 



i. Resistance measurements 767 



l^'. Experimental results on the Joule-Thomson effect 767 



1. Preliminary discussion. Methods of eliminating heat-leak. 767 



2. Discussion of the experimental results 772 



a. General 772 



b. Axial flow plugs Al, A2 and A3 777 



c. Axial flow plug A4 . 784 



d. Radial flow plugs VI and V2. The regeneration 



effect 785 



e. Radial flow i)lug S 787 



/. Measurements of juCp and the calculation of n from 



them 790 



g. The wet steam question. Radial flow plugs Ul and 



U2 793 



h. Existence of a pressure coefficient of ^ . . . . . 795 



i. Comparison with the results of other experimenters . 799 



V. Summary 803 



