TY - JOUR
T1 - Non-Fourier heat conduction in oil-in-water emulsions
AU - Liu, Fang
AU - Chen, Qiang
AU - Kang, Zhanxiao
AU - Pan, Weiguo
AU - Zhang, Dongxiang
AU - Wang, Liqiu
N1 - Funding Information:
The financial supports from the Natural Science Foundation of Shanghai in China (Grant No. 15ZR1417700 ), the Program for Professor of Special Appointment (Eastern Scholar) supported by Shanghai Institutions of Higher Learning (2013-66), “Shuguang program” supported by Shanghai Education Development Foundation and Shanghai Municipal Education Commission in China (14SG50) are gratefully acknowledged.
Publisher Copyright:
© 2019 Elsevier Ltd
PY - 2019/6
Y1 - 2019/6
N2 - Emulsions have widely been used in various application, e.g. in energy system as a potential second refrigerant. However, there is a lack of comprehensive study on extraordinary effective thermal conductivity enhancement in the oil-in-water (O/W) emulsions, and effects of temperature and droplet size were not considered in the widely used models of effective thermal conductivity for the O/W emulsions. In this study, non-Fourier heat conduction characteristics in the O/W emulsions were investigated experimentally. The O/W emulsions were prepared with different droplet sizes by controlling the ultrasonic processing time. The O/W emulsions containing small droplets are stable. Effective thermal conductivity of O/W emulsions nonlinearly varies with droplet size, concentration, fluid properties and temperature. Small droplet size is beneficial for effective thermal conductivity enhancement of O/W emulsions. Thermal conductivity of fluids can be enhanced significantly especially at low concentration although thermal conductivity of oil is much lower than water conductivity, which could be due to non-Fourier heat conductions in O/W emulsions. Time lag ratio less than 1 indicates that no thermal waves exist in O/W emulsions, and diffusion-dominant non-Fourier heat conduction could exist in the O/W emulsions. A new model of effective thermal conductivity, which considers effects of fluid thermosphysical properties, oil concentration, droplet size and temperature, was developed for the O/W emulsions based on the measured data. This study could be helpful for exploring the mechanisms behind extraordinary heat conductivity enhancement phenomena of oil-in-water emulsions.
AB - Emulsions have widely been used in various application, e.g. in energy system as a potential second refrigerant. However, there is a lack of comprehensive study on extraordinary effective thermal conductivity enhancement in the oil-in-water (O/W) emulsions, and effects of temperature and droplet size were not considered in the widely used models of effective thermal conductivity for the O/W emulsions. In this study, non-Fourier heat conduction characteristics in the O/W emulsions were investigated experimentally. The O/W emulsions were prepared with different droplet sizes by controlling the ultrasonic processing time. The O/W emulsions containing small droplets are stable. Effective thermal conductivity of O/W emulsions nonlinearly varies with droplet size, concentration, fluid properties and temperature. Small droplet size is beneficial for effective thermal conductivity enhancement of O/W emulsions. Thermal conductivity of fluids can be enhanced significantly especially at low concentration although thermal conductivity of oil is much lower than water conductivity, which could be due to non-Fourier heat conductions in O/W emulsions. Time lag ratio less than 1 indicates that no thermal waves exist in O/W emulsions, and diffusion-dominant non-Fourier heat conduction could exist in the O/W emulsions. A new model of effective thermal conductivity, which considers effects of fluid thermosphysical properties, oil concentration, droplet size and temperature, was developed for the O/W emulsions based on the measured data. This study could be helpful for exploring the mechanisms behind extraordinary heat conductivity enhancement phenomena of oil-in-water emulsions.
KW - Extraordinary effective thermal conductivity
KW - Non-Fourier heat conduction
KW - O/W emulsions
KW - Time lag ratio
UR - http://www.scopus.com/inward/record.url?scp=85061066192&partnerID=8YFLogxK
U2 - 10.1016/j.ijheatmasstransfer.2019.01.105
DO - 10.1016/j.ijheatmasstransfer.2019.01.105
M3 - Journal article
AN - SCOPUS:85061066192
SN - 0017-9310
VL - 135
SP - 323
EP - 330
JO - International Journal of Heat and Mass Transfer
JF - International Journal of Heat and Mass Transfer
ER -