TY - JOUR

T1 - Experimental studies on natural convection of water in a closed-loop vertical annulus

AU - Mustafa, Jawed

AU - Husain, Shahid

AU - Siddiqui, M. Altamush

N1 - Publisher Copyright:
© 2017 Taylor & Francis Group, LLC.

PY - 2017/1/2

Y1 - 2017/1/2

N2 - Experimental studies on heat transfer and fluid flow of water in a vertical annulus, circulating through a cold leg forming a closed loop thermo-siphon, have been carried out in this article. The annulus has a radius ratio (outer radius to inner radius) of 1.184 and aspect ratio (length to annular gap) equal to 352. The experiments were conducted for constant heat fluxes of 1, 2.5, 5, 7.5, 10, 12.5, and 15 kW/m2. Transient behavior during the heat-up period of the system until the steady-state condition is attained and discussed. Variation in the heat transfer coefficient and Nusselt number along the annulus height represent the developing boundary layer at the entrance and fully developed flow in the remaining length. A large drop in the differential pressure is experienced when the liquid is circulated through the flow meters, which restrict the flow due to their very small passages. Flow restriction causes mass accumulation and rise of pressure at the exit of the annulus. It also causes a decrease in liquid head in the cooling leg. An increase in the heat flux leads to an increase in the heat transfer coefficient and Nusselt number. As a result of the data analysis correlations for the average Nusselt number, Reynolds number and circulation rate have been developed in terms of the heat flux.

AB - Experimental studies on heat transfer and fluid flow of water in a vertical annulus, circulating through a cold leg forming a closed loop thermo-siphon, have been carried out in this article. The annulus has a radius ratio (outer radius to inner radius) of 1.184 and aspect ratio (length to annular gap) equal to 352. The experiments were conducted for constant heat fluxes of 1, 2.5, 5, 7.5, 10, 12.5, and 15 kW/m2. Transient behavior during the heat-up period of the system until the steady-state condition is attained and discussed. Variation in the heat transfer coefficient and Nusselt number along the annulus height represent the developing boundary layer at the entrance and fully developed flow in the remaining length. A large drop in the differential pressure is experienced when the liquid is circulated through the flow meters, which restrict the flow due to their very small passages. Flow restriction causes mass accumulation and rise of pressure at the exit of the annulus. It also causes a decrease in liquid head in the cooling leg. An increase in the heat flux leads to an increase in the heat transfer coefficient and Nusselt number. As a result of the data analysis correlations for the average Nusselt number, Reynolds number and circulation rate have been developed in terms of the heat flux.

KW - closed-loop thermo-siphon

KW - constant heat flux

KW - high aspect ratio

KW - natural convection

KW - radius ratio

KW - vertical annulus

UR - http://www.scopus.com/inward/record.url?scp=84988350394&partnerID=8YFLogxK

U2 - 10.1080/08916152.2015.1135202

DO - 10.1080/08916152.2015.1135202

M3 - Article

AN - SCOPUS:84988350394

SN - 0891-6152

VL - 30

SP - 25

EP - 45

JO - Experimental Heat Transfer

JF - Experimental Heat Transfer

IS - 1

ER -