AbstractOne possible nuclear reactor fuel element design consists of plate-type subassemblies cut transversely into a number of sections in the direction of flow. The use of such interrupted-plate elements should result in lower surface temperatures than full-length plate-type subassemblies by taking advantage of both a continuous entrance effect on the film coefficient of heat transfer (1) and reduced engineering hot channel factors.The purpose of this paper is to report the results of experimental investigations of the pressure drop through such interrupted-plate-type fuel elements. In particular, the joint losses between adjacent sections of a plate-type subassembly, and the entrance-pIus-exit losses on entering the initial section and leaving the final section of subassembly, have been measured as a function of Reynolds Number and, in the case of the joint losses, as a function of the spacing between the sections. Measurements have been made on six configurations; one subassembly with the plates in adjacent sections of the subassembly parallel and one with them perpendicular to each other (in-line and crossed), each subassembly being tested for the square-edged, rounded leading edge, and both ends rounded cases. Most of the measurements were made on 2 in. long sections of 2.1-in. sq. subassembly containing ten 0.087×1.82 in. plates and eleven 0.087×1.82 in. channels. The effect of longer sections was also investigated.Experimental values of dimensionless joint loss and entrance-pIus-exit loss coefficients were calculated from experimental over-all pressure drops using values for the friction factor from the literature. These experimental loss coefficients are presented graphically as a function of Reynolds Number for each configuration tested. All of the loss coefficients showed slight decreases with increasing Reynolds Number in the range tested (Reynolds Numbers from 10,000 to 100,000). Values of the joint loss coefficients are also presented graphically as a function of spacing between the sections for each configuration at a Reynolds Number of 50,000. This graph shows that the joint loss coefficients are higher than the entrance-plus-exit loss coefficients if the adjacent plate sections are square-edged and crossed, approximately the same if the adjacent sections are crossed but have rounded ends, and lower if the adjacent sections are in-line. The joint loss coefficients approach the experimental entrance-plus-exit coefficients (which agreed well with values in the literature) at large spacings, and the two were essentially equal when the spacing reached 0.05 to 0.50 in. depending on the configuration.