Design of Liquid Metal Phase Change Heat Exchanger for Next-Generation Nuclear Plant Process Heat Application

Abstract

The Next Generation Nuclear Plant will most likely produce electricity and its reactor heat will be further utilized for the production of hydrogen, oil recovery from tar sands and oil shales, and other process heat applications, that will further the nation's pursuit of energy independence. An intermediate heat exchanger is required to transfer heat from the Next-Generation Nuclear Plant to the hydrogen plant (or other processes) in the most efficient way possible. Phase change heat exchangers are quite attractive in this regard, as they can transfer process heat more efficiently than for the single phase due to the advantage of high-enthalpy transport that includes the sensible heat of liquid, the latent heat of vaporization, and possible vapor superheat. This paper explores the overall heat transfer characteristics and pressure drop of the phase change heat exchanger with helium as the primary and sodium as the secondary heat exchanger coolant. For a two-phase boiling regime, the convective heat transfer coefficient is based on the concept of an additive, interacting mechanism of micro-and macroconvective heat transfer. In this analysis an improved design is proposed for given conditions, so as to obtain a lower overall pressure drop and a moderate/high overall heat transfer coefficient. The analysis presented in this paper will be useful as a guide for future experimental work for Next Generation Nuclear Plant process heat transfer.

Thermal performance of liquid metal phase heat exchanger used in hydrogen production by thermal efficiency method

“…The heat exchange process between the superheated Helium and changing phase sodium is simulated in a heat exchanger composed of three regions, as shown in Figure 3. [1] )…”

“…Engineering and its advancements Thermal performance of liquid metal phase heat exchanger used in hydrogen production by thermal efficiency method In the two-phase flow region, Region 2, the boiling coefficient, ℎ 𝑏𝑜𝑖𝑙 , used in the simulation is associated with the nucleated boiling process, determined experimentally by W. M. Rohsenow [16] , which presumably can be applied to processes related to liquid metals, according to Piyush Sabharwall et al [1] . The Rohsenow equation is more uncomplicated and contains parameters that do not consider some complex effects, such as those occurring in convective boiling, such as that developed by J. C. Chen [17] and used by Piyush Sabharwall et al [1] . The surface tension associated with Sodium is represented by 𝜎 𝑁𝑎 and can be found in a numerical table obtained by Joanne K. Fink and Leonard Leibowitz [13] .…”

“…Note that the section length does not influence the value of the global heat transfer coefficient. The absolute deviation is the result of the simulation concerning the results presented by Piyush Sabharwall et al [1] . The results are coherent with the conditions in the simulations related to Figure 4.…”

“…When comparing the values of the global heat transfer coefficient, there is a deviation of 6.64% related to ½ the speed of sound and 9.05% for ¼ the speed of sound. The value used for comparison corresponds to the average value of the global heat transfer coefficient obtained by Piyush Sabharwall et al [1] in Region 2.…”

“…The quantities determined for global heat transfer process analysis are thermal efficiencies, thermal effectiveness, heat transfer rates, and fluid exit temperatures in the three regions described above. Piyush Sabharwall et al [1] developed a design for a heat exchanger coupled to a nuclear reactor and associated with a hydrogen production plant. The reactor supplies energy in heat to the primary helium coolant, heated to outlet temperatures of 1100 to 1300 K and flowing through a high-temperature heat exchanger, where heat exchange with Sodium occurs.…”