Measurement of the radiant heat loss from office equipment and other equipment in buildings is necessary in order to make accurate assessments of their impact on cooling loads. This paper describes a new method of measuring this heat loss that was developed as a part of ASHRAE research project RP-822, Test Method for Measuring the Heat Gain and Radiant/Convective Split from Equipment in Buildings. The measurement method, referred to here as the scanning radiometer method, utilizes a relatively inexpensive, off-the-shelf net radiometer to make the measurements. The radiometer scans a hemispherical area around the equipment being evaluated, and, by integrating the net radiant flux through this area, the total radiant flux from the equipment to the room is measured. This method automatically compensates for other radiant fluxes in the room. The radiometer sensor must be calibrated for this application, and a simple device was developed for this purpose. Before various equipment items were evaluated for radiant heat loss using the scanning radiometer method, it was tested by measuring the radiant heat losses from a heated flat plate and a heated sphere. The radiant heat loss from these well-defined objects could be calculated accurately and compared to the results obtained with the scanning radiometer measurement. In both cases, the scanning radiometer method yielded results well within the range of uncertainty in the calculated radiant heat losses. The equipment and facilities required for using the scanning radiometer method can be assembled at modest cost, and this method is recommended for future laboratory and field measurements of radiant heat loss from equipment in buildings.

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