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Spiral wound tube heat exchanger (SWHE) was confirmed as the core equipment of natural gas liquefaction (LNG). However, there was rare experimental research on large-scale SWHE for LNG, and the theory of heat transfer is not perfect. To investigate the tube-side flow and heat transfer characteristics in spiral tubes, an experimental system was proposed. To ensure the accuracy of the experimental data, the heat transfer coefficients of liquid propane under different conditions were measured, and the data acquired through the experiment were compared with two classical heat transfer correlation (Dittus–Boelter and Geielinski) under the identical working conditions. The applicability of the existing correlation was analyzed using the experimental data, and a novel heat transfer correlation was developed. As indicated by the results, the deviation between the experimental system and the classical correlation under the identical working condition was lower than ±10%. Furthermore, the error comparison between the novel correlation prediction value and the experimental data was less than ±15%. [ABSTRACT FROM AUTHOR]

The maldistribution of working medium restricts the heat transfer performance of the spiral-wound heat exchangers (SWHEs), especially when the heat exchangers are applied in floating production storage and offloading platform. Therefore, the maldistribution in the SWHEs needs to be studied under sloshing conditions. In the investigation, a novel distributor named "disc distributor" is designed and its distribution characteristic is analysed under sloshing conditions experimentally. The impacts of sloshing amplitude, sloshing periods, mass flow rate and structural parameters on flow uniformity are discussed. The results show that based on steady condition the augmentation of the sloshing amplitude makes the liquid uniformity deteriorate by 14.2–56.0%, and the enlargement of the sloshing period improves the liquid flow uniformity by 12.8–28.3%. The elevation of the mass flow rate promotes the flow uniformity by 23.8–27.0% and 13.9–32.4% under steady and sloshing conditions, respectively. The variation of hole diameter exacerbates distribution performance of the distributor by 5.3–18.4% and 2.5–22.3% under steady and sloshing conditions separately. Heave condition always has less influence on the flow uniformity of the distributor than other sloshing conditions. [ABSTRACT FROM AUTHOR]

To study the influences of phase change material (PCM) microcapsules in clothing on human thermal responses, a mathematical model is developed. The improved Stolwijk's model is used to simulate human thermo - regulatory process, and the coupled heat and moisture transfer including the moisture sorption /desorption of fibers and effects of phase transition temperature range on the phase change processes of the PCM is considered in clothing model. Meanwhile, the theoretical predictions are validated by experimental data. Then, the interactions between human body thermal responses and the heat and moisture transfer in clothing are discussed by comparing the prediction results with PCMs and without PCMs. Also the effects of fiber hygroscopicity on clothing and human thermal responses are compared. The conclusion shows that the clothing with PCMs microcapsules can delay the human temperature variations and decrease the sweat accumulation rate on the skin surface and heat loss during changing of ambient conditions, and fiber hygroscopicity reduces the effect of PCM microcapsules on delaying garment temperature variations very significantly. [ABSTRACT FROM AUTHOR]

In recent years, the use of phase change materials (PCM) to improve heat and moisture transfer properties of clothing has gained considerable attention. The PCM distribution in the clothing impacts heat and moisture transfer properties of the clothing significantly. For describing the mechanisms of heat and moisture transfer in clothing with PCM and investigating the effect of the PCM distribution, a new dynamic model of coupled heat and moisture transfer in porous textiles with PCM was developed. The effect of water content on physical parameters of textiles and heat transfer with phase change in the PCM microcapsules were considered in the model. Meanwhile, the numerical predictions were compared with experimental data, and good agreement was observed between the two, indicating that the model was satisfactory. Also the effects of the PCM distribution on heat transfer in the textiles-PCM microcapsule composites were investigated by using the model. [ABSTRACT FROM AUTHOR]

A model of simultaneous transport in hygroscopic porous materials was developed. Water in fabrics is considered to be present in three forms: liquid water in the void space between fibers, bound water in the fibers, and vapor. It is assumed that the heat and mass transport mechanisms include movement of liquid water due to the capillarity and atmospheric pressure gradient, diffusion of vapor within interfibers due to the partial pressure gradient of vapor and total gas pressure gradient, diffusion of vapor into fiber, evaporation, and condensation of water. The moisture diffusion process into hygroscopic porous materials such as wool fabrics was simulated. At normal atmospheric pressure, the results were compared with experimental data on the temperature and water content changes reported in the literature. The distribution of temperature, moisture concentration, liquid water saturation, and atmospheric pressure in the void space between fibers at different boundary conditions are numerically computed and compared. The conclusion is that atmospheric pressure gradient has significant impact on heat and mass transport processes in hygroscopic porous materials. [ABSTRACT FROM AUTHOR]

• Hydrocarbon mixtures condensation flow was investigated at heaving condition. • The simulation results coincided to experimental ones with ±15% error. • The impacts of various parameters on pressure drop and heat transfer were discussed. • Methane/ethane mixture had the best heat transfer and the smallest pressure drop. • It showed better performance at heaving condition than static one. A model based on ASNYS CFX was established to explore the pressure drop and heat transfer characteristics of condensation flow with hydrocarbon mixtures in a spiral pipe under static and heaving conditions, whose deviations are within ±15% compared to experimental ones. It considered the effects of motion parameters, operating parameters and structural parameters on frictional pressure drop and heat transfer coefficient for three hydrocarbon mixtures. The ranges of mass flux, vapor quality, heat flux, saturation pressure, hydraulic diameter, curvature diameter and inclination angle were 200–800 kg/(m2·s), 0.3–0.9, 10–20 kW/m2, 2–4 MPa, 6–14 mm, 1.6–2.4 m and 6–14°, respectively. The results demonstrate that methane/ethane mixture has the best heat transfer and the smallest pressure drop among three mixtures. At static condition, as the vapor quality and mass flux increase and the saturation pressure and hydraulic diameter decrease, there are evident increases in heat transfer and pressure drop, whereas the impacts of curvature diameter, inclination angle and heat flux on them are insignificant. Meanwhile, the heaving motion affects pressure drop and heat transfer and makes it show better overall heat transfer performances, where the comprehensive heat transfer factors (CHFs) of 83.33% data points are more than 1. Further, the heaving effects increase with the increasing heaving amplitude and the decreasing heaving cycle. [ABSTRACT FROM AUTHOR]

Highlights • A model was established to investigate condensation flow under sloshing condition. • The influence of different parameters on pressure drop and heat transfer was studied. • The comprehensive effects of sloshing conditions were analyzed. • Sloshing conditions little affect pressure drop, but obviously affect heat transfer. • The heaving condition has the maximum effects on flow and heat transfer among others. Abstract In order to explore condensation flow and heat transfer characteristics in the tube side of spiral wound heat exchange (SWHE) used in floating liquefied natural gas (FLNG) field, a model was established to simulate methane condensation upward flow in a spiral pipe at different sloshing conditions, such as heave, roll and pitch conditions. The simulated results coincide with experiment ones, and the deviations are within ±15%. The effects of various parameters on frictional pressure drop and heat transfer coefficient were discussed in pipes with curvature ratio of 0.003–0.007. The ranges of Reynolds numbers in vapor and liquid flows are respectively 154,944–697,251 and 18,190–127,331. It was found that at static conditions, both frictional pressure drop and heat transfer coefficient increase with the increase of mass flux and the decrease of saturation pressure and hydraulic diameter; with the increase of vapor quality, the heat transfer coefficient first increases and then decreases whereas the frictional pressure drop continuously increases; the effects of curvature diameter are slight. Meanwhile, in most cases, the sloshing motions can cause a remarkable heat transfer enhancement as well as a small decrease of frictional pressure drop. Further, the effects of heaving motion on flow and heat transfer are more obvious than the others, with the average drag reduction and heat transfer augmentation of 1.51% and 15.70%, respectively. These results are helpful for the understanding condensation characteristics in the spiral pipe at sloshing conditions, and for the design of SWHE used in FLNG field. [ABSTRACT FROM AUTHOR]

In this paper, the condensation heat transfer of hydrocarbon mixtures refrigerant (methane/propane) flowing in a helical tube with 10 mm hydraulic diameter was investigated by experiments and numerical simulations. The experiments were conducted at mass flux of 200–400 kg/(m 2 ·s), saturation pressure of 0–4Mpa and heat flux of 4.8–5 kW/m 2 . Also, the effects of mass flux, vapor quality, and saturation pressure on heat transfer coefficient were studied. It was observed that the heat transfer coefficients increased with the increase of mass flux and vapor quality, while the heat transfer coefficients generally decreased as the saturation pressure increased. Meanwhile, annular flow(half-annular flow, annular flow) and Non-annular flow patterns (slug flow, stratified flow, wavy flow, transition flow) were observed during the condensation of methane/propane mixtures refrigerant. And a new flow pattern transition line for hydrocarbon refrigerants condensation process was proposed. The condensation heat transfer coefficient data were compared with several existing correlations, and a modified heat transfer correlation for different flow patterns was proposed, which predicted the results well with a mean absolute error of 10.03%. [ABSTRACT FROM AUTHOR]

Helical tube has been widely used in liquefied natural gas (LNG) liquefying applications. However, studies on the heat transfer performance of hydrocarbon mixture refrigerant in a helical tube have rarely been conducted. In this paper, condensation heat transfer characteristics of hydrocarbon mixture refrigerant in a helical tube were investigated numerically. The tests were conducted at saturation pressure of 2–4 MPa, mass flux of 100–400 kg/(m 2 ·s) and vapor quality 0–1. The numerical model was well verified by experimental data. And the effects of different structural parameters (tube diameter, helix angle and curvature diameter) and operating parameters (mass flux, heat flux and saturation pressure) on the heat transfer of hydrocarbons refrigeration were considered. The results showed that the tube diameter and mass flux had significant effect on condensation heat transfer coefficient. Meanwhile, stratified flow, half-annular flow and annular flow were observed during the condensation of methane/propane mixtures refrigerant by simulations, and a new flow pattern transition line for hydrocarbon refrigerants condensation process was proposed. Finally, the simulation results were compared with several well-known condensation heat transfer correlations. The research results will provide some constructive instructions for more effective design of LNG heat exchanger. [ABSTRACT FROM AUTHOR]