The kata-thermometer as a measure of ventilation

In two papers previously published, one by Leonard Hill, O. W. Griffiths and M. Flack, and the other by Leonard Hill and D. Hargood-Ash, the kata-thermometer was described in detail, and formulæ were given connecting the heat loss with temperature, wind velocity and vapour pressure. Various discrepancies were found to occur, however, and seeing that the kata-thermometer has become recognised as a measure of ventilation the whole matter has now been carefully reinvestigated. Large wind tunnels such as those at the National Physical Laboratory, which were not available during the war, owing to the urgency of aeroplane work, were now at our disposal. Experimental Work. To obtain known wind velocities for the experimental work two methods were adopted, that of the “wind tunnel” where the air is drawn through a long tunnel by means of a propellar at one end, and that of the “whirling arm” where the “kata” is made to move through the air on a revolving arm. The wind tunnel work was carried out in the engineering department at the National Physical Laboratory by kind permission of Dr. T. E. Stanton, where Miss D. Marshall gave us valuable assistance in the determination of wind velocities; also at East London College, where Dr. N. A. V. Piercy was good enough to allow us the use of the tunnel and to help us in determining the wind velocities.