TY - JOUR
T1 - Heat transfer measurement and flow regime visualization of two-phase pulsating flow in an evaporator
AU - Yang, Peng
AU - Zhang, Yuheng
AU - Wang, Xiaofei
AU - Liu, Ying wen
N1 - Funding Information:
The authors gratefully acknowledge the support provided by the Air Conditioning and Refrigeration Center at the University of Illinois at Urbana-Champaign. Dr. Yang also wants to acknowledge the support from the China Scholarship Council.
Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2018/12
Y1 - 2018/12
N2 - Heat transfer and flow regime of two-phase R134a pulsating flow in an evaporator have been studied experimentally in this work. Heat transfer coefficient was measured and liquid-vapor two-phase flow regimes was observed under different mass flux, inlet vapor quality and pulsating period. Results show that heat transfer can be enhanced by pulsating flow in short periods (<16 s) with a maximum enhancement of 28% compared with the continuous flow; a deterioration of heat transfer is also observed for flow under long pulsating periods for some conditions, which could be as much as 30%. The effect of mass flux and inlet vapor quality is complex and coupled with pulsation period, which might result from the difference of flow developing between different pulsating periods. The instantaneous flow regime is recorded by a high speed camera and statistically analyzed to explore the mechanism of pulsating flow on heat transfer performance. The statistical analysis of flow regime from the recorded video shows that the flow regime of pulsating flow at on-time remains the same as that of continuous flow with the same instant mass flux, and the flow regime at off-time is mostly stratified, stratified wavy flow depending on the pulsating period. The transition of stratified-wavy flow regime to intermittent, annular flow regime of pulsating flow is the main contribution to the enhancement of heat transfer while dry-out during off-time plays an important role in heat transfer deterioration.
AB - Heat transfer and flow regime of two-phase R134a pulsating flow in an evaporator have been studied experimentally in this work. Heat transfer coefficient was measured and liquid-vapor two-phase flow regimes was observed under different mass flux, inlet vapor quality and pulsating period. Results show that heat transfer can be enhanced by pulsating flow in short periods (<16 s) with a maximum enhancement of 28% compared with the continuous flow; a deterioration of heat transfer is also observed for flow under long pulsating periods for some conditions, which could be as much as 30%. The effect of mass flux and inlet vapor quality is complex and coupled with pulsation period, which might result from the difference of flow developing between different pulsating periods. The instantaneous flow regime is recorded by a high speed camera and statistically analyzed to explore the mechanism of pulsating flow on heat transfer performance. The statistical analysis of flow regime from the recorded video shows that the flow regime of pulsating flow at on-time remains the same as that of continuous flow with the same instant mass flux, and the flow regime at off-time is mostly stratified, stratified wavy flow depending on the pulsating period. The transition of stratified-wavy flow regime to intermittent, annular flow regime of pulsating flow is the main contribution to the enhancement of heat transfer while dry-out during off-time plays an important role in heat transfer deterioration.
KW - Heat transfer enhancement ratio
KW - Liquid-vapor two phase flow regime
KW - Pulsating flow (pulsed flow)
KW - Pulsating period
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U2 - 10.1016/j.ijheatmasstransfer.2018.08.065
DO - 10.1016/j.ijheatmasstransfer.2018.08.065
M3 - Article
AN - SCOPUS:85052338212
VL - 127
SP - 1014
EP - 1024
JO - International Journal of Heat and Mass Transfer
JF - International Journal of Heat and Mass Transfer
SN - 0017-9310
ER -