Transient Heat Transfer Characteristics Research Articles

Transient behaviour and heat transfer characteristics in debris beds: Simulation and analysis of the LIVEJ2 experiment

Multiple uncertainties still exist about the state of the debris in Fukushima Daiichi Nuclear Power Station (1F). In the past, the attention of the nuclear safety community was focused on the heat transfer characteristics in the case of an homogeneous pool, but little attention was given to address the melting and heat transfer in the presence of a debris bed constituted of materials with different melting points. This condition represents a challenge for CFD analyses, because it includes multi-physics conditions, such as a low melting point fluid convecting into a debris bed surrounded by a crust on the vessel wall which has received little attention compared to classical CFD analyses. Even though a comprehensive analysis of a related experiment (i.e. LIVE-J2) has been performed recently by Madokoro et al. (2023) little attention on the results has been paid to the effect of debris bed porosity and the existence of a gap between the vessel wall and the crust. In the paper we have modified the porosity resistance based on the Ergun equation and proposed a simple model for the gap conductance in the lower part of the crust. The results show an improvement in the prediction of the thermal stratification and the vessel temperature in the lower locations. In addition, highlight that such phenomena constitute key parameters to keep into consideration in the simulation of prototypical cases both for CFD and lumped parameter codes (e.g. MELCOR, MAAP).

Transient flow and heat transfer characteristics of single-phase nanofluid past a stretching sheet under the influence of thermal radiation and heat source

This work aims to investigate the unsteady hydromagnetic free convective flow of a viscous, electrically incompressible fluid influenced by an inclined magnetic field, radiation, and heat source. Specifically, it explores the behavior of water-based nanofluids under these conditions. The Newton-Raphson shooting technique combines the 4th-order Runge-Kutta approach to obtain dimensionless and accurate solutions to the governing equations. The study assesses flow characteristics and heat transfer properties over various parameter values. The outcomes are visualized through graphical representations of velocity, temperature, skin friction coefficient, and the local Nusselt number. The present study examines the impact of copper (Cu), silver (Ag), alumina (Al2O3), and titanium dioxide (TiO2) nanoparticles in water as the base fluid on the percentage increase in skin friction and Nusselt number under various physical conditions. Suction increases skin friction by 10–15 % and the Nusselt number by a similar margin, whereas injection can reduce these metrics. Radiation enhances heat transfer, resulting in a 5–10 % increase in skin friction and a 10–15 % rise in the Nusselt number, with nanoparticles like Ag showing the most substantial effects due to their superior thermal properties.

Fast cooling miniature Joule-Thomson cryocooler with improvement of energy recovery and thermal mass distribution

Open-cycle conical miniature J-T cryocoolers are favored for applications in the infrared detection field, due to their fast cooling and compact lightweight features. In this type of cryocooler, the regenerative heat exchanger for energy recovery plays a vital role in both its miniaturization and fast cool-down, because its geometry greatly determines the distribution of its heat transfer area and thermal mass. To examine and optimize the effects of the geometry on its fast-cooling performance, a validated transient analysis model, being capable of simulating the entire operating process of an open-cycle miniature J-T cryocooler, was applied to analyze and compared the transient heat transfer and flow characteristics, and then the cooling performance under different operating conditions for one cylindrical and three different cone-angle J-T cryocoolers in this study. Researches show that in terms of geometry, it is advisable to increase the heat transfer area near the cold end of heat exchanger while ensuring a relatively small thermal mass for the entire cryocooler. By analysis, a novel structure of heat exchanger with reduced volume and mass was proposed to enhance the fast-cooling performance and miniaturize cryocooler. Studied results indicate that the performance of this novel cryocooler is improved in terms of reducing the cool-down time by 28% and the volume by 50%. Additionally, this optimized structure exhibits excellent fast-cooling performance under broader operating conditions.

Investigation of the unsteady thermal storage performance of metal foam dual-phase change unit thermal storage tanks in solar thermal utilization systems

The adoption of metal foam thermal energy storage (TES) tanks in solar thermal utilization systems is crucial for enhancing energy supply stability. In this study, to investigate the transient thermal storage performance of TES tanks, a model of a solar thermal utilization system integrated with solar collectors and TES tanks was established. The model was validated through a literature review and experiments. The effects of initial temperature variation of solar collectors and the addition of metal foam on the transient heat transfer characteristics and thermal efficiency of TES tanks were analyzed. The results indicate that the porous structure of metal foam restricts natural convection, thereby improving temperature drift caused by displacement due to phase change material density variation. Maintaining the same initial temperature of solar collectors, filling metal foam can avoid the occurrence of melting dead zones at the bottom of pure paraffin phase change units, leading to an enhancement in the thermal efficiency of TES tanks and a reduction of 48.44% in phase change completion time. Additionally, a low initial temperature of the solar thermal collection system contributes to improving the thermal efficiency of metal foam composite TES tanks.

Effect of vertical vibration on transient heat transfer characteristics of flow boiling in small rectangular channels

In the thermal management of fuel cell vehicles, radiators are subjected to vibrations due to vehicle speed and road surface irregularities. However, there has been no comprehensive study of the impact of these vibrations on the heat transfer performance of radiators. Therefore, this paper employs R141b to conduct three-dimensional transient numerical simulations of flow boiling in small channels under vertical vibrations. The study reveals that the single-phase heat transfer coefficient exhibits periodic variations. At the same vibration frequency, the heat transfer frequency for the vertically oriented heating surface is twice that of the horizontally oriented surface, This is because the thermal boundary layer varies with the vibration velocity. Furthermore, as the frequency increases to 21 Hz, the time-averaged heat transfer coefficient can increase by up to 2.5 times. Following boiling onset, for horizontally oriented heating surfaces, an increase in frequency or amplitude enhances the transient heat transfer performance. Under the conditions of 28 Hz and 5 mm, the heat transfer coefficient can increase by 125.7%. However, for vertically oriented heating surfaces, when the frequency exceeds 14 Hz or the amplitude exceeds 8 mm, the heat transfer performance weakens after 7.143 s due to the promotion of bubble coalescence by the vibrations.

Transient heat transfer and deformation characteristics of a bidirectional compressor cylinder block-piston assembly under multi-field coupling

This paper established a multi-field coupling model for the air-cooled cylinder-piston assembly of a bidirectional compressor, proposed a transient calculation method, studied the temperature and deformation characteristics of each component in a single working cycle, constructed five evaluation indexes, analyzed the internal temperature and deformation characteristics of the cylinder block-piston assembly, explored the effect of different loads on the deformation, and verified the reasonableness of the method through tests. The results show that the research method of this paper is relatively accurate, and the calculation error is within 7 %; during a single working cycle, the temperature of each component shows a “W”-type change, and the maximum deformation shows a “folding” type change; the average temperature and maximum deformation of each component are highest at crank angles of 184° and lowest at crank angles of 101°; under extreme working conditions, the temperature and deformation of all parts are distributed in a “tilted” manner, with the percentage of the hot zones in the cylinder block as high as 54.6 %, and the thermal load plays a dominant role in the deformation of the cylinder-piston assembly; the average abnormal deformation at the position of support ring 1 reached 0.039 mm, which is very likely to cause wear and air leakage.

Numerical study on transient coke deposition and heat transfer characteristics of hydrocarbon fuel in a mini-channel under varying wall heat flux

Dynamic coke deposition has significant influence on flow and heat transfer characteristics of regenerative cooling using hydrocarbon fuel. In the present work, the effect of coke deposition on flow and heat transfer performance of hydrocarbon fuel, n-Decane is numerically investigated under different heating modes including the constant heat flux (CHF), the periodic heat flux (PHF) and staged heat flux (SHF). The results show that as the heating mode varies from CHF to SHF, locally high temperature zones are formed. The flow field structure is varied by dynamic heating condition and coke deposition. The reaction rate of n-Decane also varies periodically with heat flux, resulting in an irregular “S” shaped density distribution. The two main coke precursors i.e., propylene and aromatics are highly sensitive to temperature due to secondary reactions. The thickness of coke deposition increases significantly with time regardless of the heating modes, which indicates that coke deposition process is irreversible. Compared with CHF heating mode, the thickness of coke deposition increases by nearly 25% for the SHF heating mode. Coking mechanism undergoes transition from catalytic coke to lateral coke with increasing temperature. For the CHF heating mode, the heat transfer coefficient increases from 1200 W/(m2·K) to 4400 W/(m2·K) along the flow direction. The PHF and SHF heating modes render higher Nusselt number and heat transfer coefficient than the CHF heating mode as the periodically varying wall heat flux results in locally higher heat flux and smaller temperature difference between the fluid and solid zones. In addition, the thermal conductivity and flow velocity in the regenerative cooling channel are also enhanced for the PHF and SHF heating modes. However, coke deposition leads to serious heat transfer deterioration for PHF and SHF with a decrease of up to 13% in heat transfer coefficient adjacent to the outlet section of the cooling channel. The new heat transfer correlation considering chemical reaction and coke deposition effects of supercritical hydrocarbon fuel is established for different wall heating conditions.

Transient thermal behavior and efficiency in fully wet porous longitudinal fin: The influence of shape-dependent hybrid nanofluid and internal heat generation

The main focus of this study is to analyze the transient heat transfer characteristics of a convective–radiative longitudinal porous fin fully wetted in hybrid nanofluid along with internal heat generation. The Darcy formulation is considered for analyzing the velocity of the fluid passing through the fin and the Rosseland approximation determines the radiation heat flux. The hybrid nanofluid is obtained by immersing GO and Mo S 2 nanoparticles in the hybrid base fluid C 2 H 6 O 2 ‐ H 2 O . Furthermore, three different shapes of nanoparticles namely spherical, platelet, and blade have been selected for the investigation. The derived nonlinear partial differential equation is nondimensionalized and solved numerically by employing the finite difference method. The effect of shape factor, nanoparticle volume fraction, dimensionless time, wet porous parameter, radiation–conduction parameter, heat generation parameters, and other relevant parameters on the transient thermal analysis of the fin structure has been graphically analyzed and discussed. Furthermore, the transient thermal fin efficiency has been modeled and its variation with the significant parameters has been examined. One of the major outcomes is that efficiency increases with nanoparticle volume fraction. The examination has resulted in a novel outcome that the presence of hybrid nanofluid enhances the fin efficiency and also the high fin efficiency is achieved in the presence of blade-shaped nanoparticles. The findings of the investigation play a prominent role in the heat transfer enhancement of industrial processes.

Convective heat transfer of falling film around the horizontal half-oval tube with reverse airflow in an evaporative condenser

Horizontal falling-film evaporation is frequently used in industrial air conditioning system to improve its thermal performance. Transient heat transfer characteristics on the surface of a circular tube have been investigated, while the non-circular tube such as half-oval tube has been rarely reported. This study aims to investigate the thermal performance of liquid film around a half-oval tube by adopting transient simulations with laminar and SST k-ω models, respectively. Simulations consider varying wind velocity, liquid Reynolds number, heat flux and length-width ratio of the tube. Simulated results are quantitively validated by comparing with reported experimental results, and the average differences are below 9.5 %. Results indicate that the local convective heat transfer coefficient (CHTC) increases with wind and the average CHTC is at least 5.98 % higher than the case without wind. Although the influences of liquid Reynolds number and heat flux show slight differences, they still can improve the convective heat transfer. The local CHTC exhibits an escalating trend with length-width ratio of 1–5. Meanwhile, the average CHTC for the four tested half-oval tubes is at least 6.8 % higher than the values of the circular tube. An empirical correlation for predicating the average CHTC is established by regression fitting with a mean deviation of 4.6 %. These findings help to design the falling-film evaporation system by adopting the half-oval tube in industrial air conditioning system.

Heat transfer performance of high-temperature heat pipe startup in small heat pipe reactors

High-temperature heat pipe is an important heat transfer component in small heat pipe reactors (SHPR). Research on the transient heat transfer characteristics during heat pipe startup is crucial for safety analysis of SHPR. This manuscript investigates the startup performance of a lithium heat pipe from the frozen state with various influencing factors, including heating power, inclination angle, and convection heat transfer coefficient. The objective of this work is to speed up the heat pipe startup process in a safe and economic manner based on its heat transfer characteristics. In order to illustrate the startup characteristics and further to reduce the startup time, this manuscript constructs a CFD heat pipe model via the multi-physics simulation software, COMSOL. The phase change process of heat pipe startup is described by the Phase Change Material method, with the fluid velocity and pressure fields of wick established using the Brinkman equation. Results show that the heat pipe thermal resistance decreases with increasing heating power, positive inclination angle, or convection heat transfer coefficient. On the other hand, the heat pipe startup time reduces with increasing heating power, increasing positive inclination angle, or decreasing convection heat transfer coefficient. Moreover, numerical analysis indicates that heat pipe temperature rises faster in the evaporation section than in the condensation section at the beginning of startup. Temperature rise process in the condensation section occupies the majority of the entire heat pipe startup process. Therefore, to speed up the startup process, this work proposes a novel extra heating method applying to the condensation section at early startup. Compared with the conventional startup, the proposed method is able to shorten the startup time by 10.5 % and 15.8 % with an extra heating power of 10 % Full Power (FP) and 20 %FP respectively.

Characteristics of the transient heat transfer of impinging flames and correlation analysis using a new characteristic velocity under CI engine-like conditions

Understanding the transient heat transfer mechanism of impinging flames is a crucial pathway for further improving the thermal efficiency of already efficient compression ignition (CI) engines. In this paper, the investigation of the transient heat transfer of wall-impinging flames was performed in a high-pressure constant-volume vessel. Fast-response thermocouples were installed in the impinging wall to record the transient heat flux. Two-color pyrometry was employed to estimate the mean temperature inside the flame region. Firstly, the transient heat transfer characteristics were investigated under varied ambient density, oxygen concentration, temperature, and injection pressure conditions. The optical flame velocity calculation method was applied to this extensive dataset to develop a heat transfer correlation between Nu and Re with which transient heat transfer coefficients were calculated and compared with the experimental results. From this analysis, cumulative fuel injection velocity was developed as the new characteristic parameter to characterize the transient heat transfer of the wall-impinging flames. Results indicate that the effect of fuel injection pressure on the heat flux is more significant than that of ambient gas conditions, with higher injection pressure causing higher heat flux through the impinging wall. No obvious linear tendency of transient Nu and Re was found when using the optical measurement results of the wall-impinging flame as the characteristic parameter. Instead, the cumulative fuel injection velocity shows a strong linear trend of transient Nu and Re during the transient heat transfer processes of the wall-impinging flame. Moreover, the heat transfer coefficients from the new cumulative fuel injection velocity well fit the experimental results.

Numerical investigation of subcooled two-phase flow and heat transfer characteristics in a liquefied natural gas cargo containment system

The increase demand in liquefied natural gas (LNG) leads to an increase in the import and export of LNG cargo using LNG carriers with composite insulation and double-hull structures for membrane-type storage tanks. Therefore, the transient characteristics of cryogenic heat transfer in LNG cargo containment systems have become important for understanding the physics when LNG vaporizes into the gas phase to minimize the cargo loss of boil-off gas (BOG). However, public papers on fundamental research on long-term computational fluid dynamics (CFD) simulations are still lacking. In the present study, the transient flow behaviors of LNG fluids and the heat transfer characteristics were numerically studied by applying the simplified single-layer insulation in an LNG cargo containment system, based on an initial temperature of TLNG,0 = 110.5 K and saturation temperature of TLNG,sat = 111.5 K in the boundary condition of IGC code. The proposed analysis procedure can serve as a reference for relative comparison of predicted BOG difference in LNG cargo holds.Consequently, the heat transfer mode between the two-phase methane and the solid insulation could be typically classified into two different regimes: (1) a subcooled regime before reaching the saturation temperature from the initial temperature, and (2) a boiling regime after reaching the saturation temperature. In the subcooled regime, the subcooled liquid exhibited bulk flow motion induced by natural convection. The loss rate of LNG mass per time interval was extracted from the best-fit correlations as −0.0448 kg/s at 1 d (105 s) to cool down the insulation system and −0.0072 kg/s at 5 d (5 × 105 s) to reach the LNG saturation temperature. When the predicted value of the loss rate of LNG mass by the CFD simulation was regarded as the generation rate of boil-off gas, it was smaller than the designed value of the boil-off gas of 0.464 kg/s corresponded to boil-off rate (BOR) about 0.2 %/day. In the boiling regime and under sufficiently cooled conditions, the loss rate of LNG mass per time interval did not consistently exceed the BOR value. The liquid flow exhibited a turbulent-like motion despite the relatively low velocity at 10 d (106 s). Especially, the increase in the effective thermal conductivity was a good indicator for distinguishing between the boiling and subcooled regimes.

Transient thermal analysis of the rotary compressor during startup process

The transient temperature distribution and heat transfer characteristics of the rotary compressor are crucial to its reliability and efficiency of the compressor. In this paper, a transient mathematical model on predicting the temperature in the compressor during startup is proposed. Control volumes are divided including the fluid and solid domains. The convective heat transfer coefficient of each surface is discussed. A coupled solution method and its Fortran calculation program are developed. This mathematical model is experimentally validated by comparing the measured and calculated temperatures of the compressor. The results shows that calculated temperatures are consistent with the measured results during the startup process. The maximum error of the steady-state temperature is within 2 °C. The refrigerant in the compression unit mainly absorbs heat from the refrigerant in the lower chamber. Measures should be taken to reduce the heating of the upper bearing surface by the refrigerant in the lower chamber to improve the volume and indicated efficiencies.

Experimental Validation of a Numerical Coupling Environment Applying FEM and CFD

Experimental results for the transient heat transfer characteristics over a flat plate and over a plate with V-shaped ribs were compared to numerical results from a coupling environment applying FEM and CFD. In order to simulate transient effects in the cooling process of engine components during typical flight missions, the temperature and the velocity at the inlet of the channel were varied over time. The transient temperature distribution at the plate was measured using infrared thermography. Five different plate materials (perspex, PEEK, quartz, aluminum, and steel) were considered to investigate the influence of thermal conduction on the heat transfer between solid and fluid depending on the Biot number. The experimental results represent a reference database for a Python-based coupling environment applying CalculiX (FEM) and ANSYS CFX (CFD). The results were additionally compared to numerical results simulating the complete transient conjugated heat transfer with CFD. A good agreement between the numerical and the experimental results was achieved using different coupling sizes at different Biot numbers for the flat plate and the plate with V-shaped ribs.

Development and validation of the helically coiled steam generator model of RELAP5/MOD3.4 code

The flow field and heat transfer characteristics in a helical coil tube-type once-through steam generator (HCOTSG) are more complex than those in a straight pipe-type steam generator owing to the complex geometry of the former and the secondary flow induced by the centrifugal force. Straight tube heat transfer correlations and pressure correlations unapplicable for helical coils. System analysis codes used in design and safety analysis of HCOTSG are still missing. In this study, a code called RELAP5/MOD3.4-HCOTSG was developed for a numerical simulation of an HCOTSG based on the RELAP5/MOD3.4 code, and on suitable empirical correlations of the heat transfer coefficients and pressure drop chosen for HCOTSG. The code is first validated through a comparison with the IRIS HCOTSG design parameters, and the results indicate that the chosen models can accurately simulate the wall heat transfer and achieve a higher accuracy in the wall friction pressure drop prediction. Based on this, an analysis of typical transients is conducted to evaluate the transient characteristics of IRIS HCOTSG. The results indicate that the RELAP5/MOD3.4-HCOTSG code has the ability to calculate the transient flow and heat transfer characteristics of an HCOTSG and can serve as an analysis tool for the system calculation of a small modular reactor.

An inverse analysis to estimate the thermal properties of nanoporous aerogel composites using the particle swarm optimized deep neural network

To understand the transient heat transfer characteristics of nanoporous aerogel insulating composites, solving the inverse heat transfer problem would be crucial for identifying the temperature-dependent thermal properties of composites. In this study, with constructed a forward model to numerically investigate the heat transfer in composites, a deep neural network (DNN) model and a particle swarm optimized deep neural network (PSO-DNN) model are conducted to rapidly estimate the effective temperature-dependent thermal conductivity of the desiccated and moist composites from the temperature response measurements. With the DNN model, the retrieved thermal conductivities for desiccated composites possess low deviation to experimental measurements (<3.2%) and constantly low errors (<5.2%) from 280 K to 1080 K. The precision of the DNN solver could be enhanced by adjusting the hyperparameters of the neural networks using PSO. The retrieved thermal conductivities possess low deviation from experiments (<2.5%) and low relative errors within 1.5%. Furthermore, the robustness of the PSO-DNN solver is discussed when commercial thermocouple measurement errors are considered, within retrieving the thermal properties of desiccated and moist aerogel composites.

Modeling and techno-economic comparison of two types of coaxial with double U-tube ground heat exchangers

Among different types of ground heat exchangers (GHEs), multi-external chamber coaxial GHE is recently a promising design due to its geometrical characteristics of concentric tube-in-tube configuration and maximal heat exchange performance. Nevertheless, the characterization and commercialization of multi-external chamber coaxial GHEs need a deep understanding of the effect of different opt-geometrical and operational parameters on their thermo-economic performance. Therefore, accurate numerical modeling of the transient heat transfer proficiencies and the techno-economic feasibility of the multi-external chamber coaxial GHE and coaxial GHE compared to conventional double U-tube GHE is crucial to promise an optimal design of ground-coupled heat pump systems. This study introduces a comprehensive systematic and techno-economic analysis of the transient heat transfer characteristics of coaxial and multi-external-chamber coaxial GHEs compared to conventional double U-tube GHE. A three-dimensional numerical model was adopted and validated by field experiments. Moreover, a sensitivity analysis was conducted to investigate the impacts of several key operating and design parameters on heat transfer performance under heating and cooling modes conditions. Furthermore, various case studies, along with a comprehensive analysis of multi-objective optimization for minimization of the GHE number and energy consumption, were also carried out. In addition, a techno-economic analysis was also carried out using the total annual cost method to assess the economic viability of the proposed GHE designs. The results reveal that, compared to double U-tube GHE, coaxial GHE has the best thermal performance with maximum and average heat transfer rates of 127.54% and 17.67%, while the multi-external-chamber coaxial GHE is estimated to be 62.38% and 11.72%, respectively. Also, the corresponding total thermal resistance of coaxial GHE is the lowest by 14.86%, and for multi-external-chamber coaxial, it is 10.30%; also coaxial GHE has the lowest pressure drop by 76.45%, followed by multi-external-chamber coaxial GHE with 57.18%. In the case studies, replacing double U-tube GHE with coaxial or multi-external-chamber coaxial GHEs, the GHE number can be decreased by 13.3% for both the designs, or the energy consumption of the water pump by 33.91% and 30.97%, and the energy consumption of the entire system by 17.21% and 10.54%, respectively. The techno-economic analysis results indicate that replacing double U-tube GHE with coaxial GHE is the most feasible alternative, which can decrease the total annual cost by 13.58%, followed by multi-external-chamber coaxial GHE by 6.77%. Further discussion for the deep applications was performed, which concluded the optimal GHE design. The findings of this paper can be used as a guide for future research on GHEs for potential applications of ground-coupled heat pump systems.

Transient heat transfer characteristics in spray cooling

Transient heat transfer characteristics in spray cooling

Experimental study on transient heat transfer characteristics during the dropping of containment pressure

The reactor containment integrity and the pressure inside the containment are the most concern in the practical running process. To evaluate the transient heat transfer, non-equilibrium fraction (NEF) is proposed to represent the completed degree of transient condensation. An empirical correlation for NEF is developed and the fit error is within ±25% for 97% of results. Based on this, a simplified calculation model for transient heat transfer rate is also developed, then the transient condensation heat transfer coefficient (HTC) is obtained to characterize the intensity of transient heat transfer. The effect of mixed gas pressure, air mass fraction and temperature of cooling water on NEF and transient condensation HTC are discussed. The result indicates that the initial air mass fraction and initial gas-mixture pressure play an important role in transient-state heat transfer, and the influence of initial cooling water temperature can be ignored. This study aims to improve the understanding of transient-state heat transfer and provide guidance to practical engineering.

Effects of rolling motion on flow and heat transfer characteristics in a tube bundle channel

The usage of nuclear energy in the ocean is growing, and the most significant fundamental motion of ocean conditions is rolling motion. Due to the significant quantity of tube bundle channels in marine nuclear power equipment, it is crucial to investigate the single-phase and boiling heat transfer characteristics in tube bundle channels under rolling motion. The paper compares the single-phase convection, sub-cooled boiling, and saturated boiling heat transfer characteristics under rolling and vertical conditions. The result demonstrates that the two-phase time-averaged heat transfer is lower under rolling motion compared with that under vertical conditions, and the rolling motion has the strongest impact on the time-averaged sub-cooled boiling. Time-averaged heat transfer coefficient decreases with the increase of the rolling amplitude and period. Due to the dearth and the necessity of research on transient sub-cooled boiling under rolling motion, the instantaneous sub-cooled boiling heat transfer fluctuation characteristics are investigated. The fluctuation amplitude of the heat transfer coefficient increases with increasing rolling period and frequency. The change of bubble behavior caused by rolling motion is the main reason for the change of transient heat transfer characteristics compared with that under vertical conditions. At last, a series of correlations based on the Gungor-Winterton correlation is improved and proposed to predict the instantaneous sub-cooled boiling heat transfer coefficient. Thereinto, the average relative error is 7.36% for forecasting the time-averaged heat transfer coefficient, and the average relative error for predicting the fluctuation amplitude of the heat transfer coefficient is 11.58%.