Experimental Study on the Heat Transfer Performance of Pump-Assisted Capillary Phase-Change Loop

To overcome the two-phase flow instability of traditional boiling heat dissipation technologies, a porous wick was used for liquid-vapor isolation, achieving efficient and stable boiling heat dissipation. A pump-assisted capillary phase-change loop with methanol as the working medium was established to study the effect of liquid-vapor pressure difference and heating power on its start-up and steady-state characteristics. The results indicated that the evaporator undergoes four heat transfer modes, including flooded, partially flooded, thin-film evaporation, and overheating. The thin-film evaporation mode was the most efficient with the shortest start-up period. In addition, heat transfer modes were determined by the liquid-vapor pressure difference and power. The heat transfer coefficient significantly improved and the thermal resistance was reduced by increasing liquid-vapor pressure as long as it did not exceed 8 kPa. However, when the liquid-vapor pressure exceeded 8 kPa, its influence on the heat transfer coefficient weakened. In addition, a two-dimensional heat transfer mode distribution diagram concerning both liquid-vapor pressure difference and power was drawn after a large number of experiments. During an engineering application, the liquid-vapor pressure difference can be controlled to maintain efficient thin-film evaporation in order to achieve the optimum heat dissipation effect.

Raf-like kinases and receptor-like (pseudo)kinase GHR1 are required for stomatal vapor pressure difference response

Stomatal pores close rapidly in response to low-air-humidity-induced leaf-to-air vapor pressure difference (VPD) increases, thereby reducing excessive water loss. The hydroactive signal-transduction mechanisms mediating high VPD–induced stomatal closure remain largely unknown. The kinetics of stomatal high-VPD responses were investigated by using time-resolved gas-exchange analyses of higher-order mutants in guard-cell signal-transduction branches. We show that the slow-type anion channel SLAC1 plays a relatively more substantial role than the rapid-type anion channel ALMT12/QUAC1 in stomatal VPD signaling. VPD-induced stomatal closure is not affected in mpk12/mpk4GC double mutants that completely disrupt stomatal CO2 signaling, indicating that VPD signaling is independent of the early CO2 signal-transduction pathway. Calcium imaging shows that osmotic stress causes cytoplasmic Ca2+ transients in guard cells. Nevertheless, osca1-2/1.3/2.2/2.3/3.1 Ca2+-permeable channel quintuple, osca1.3/1.7-channel double, cngc5/6-channel double, cngc20-channel single, cngc19/20crispr-channel double, glr3.2/3.3-channel double, cpk-kinase quintuple, cbl1/4/5/8/9 quintuple, and cbl2/3rf double mutants showed wild-type-like stomatal VPD responses. A B3-family Raf-like mitogen-activated protein (MAP)-kinase kinase kinase, M3Kδ5/RAF6, activates the OST1/SnRK2.6 kinase in plant cells. Interestingly, B3 Raf-kinase m3kδ5 and m3kδ1/δ5/δ6/δ7 (raf3/6/5/4) quadruple mutants, but not a 14-gene raf-kinase mutant including osmotic stress-linked B4-family Raf-kinases, exhibited slowed high-VPD responses, suggesting that B3-family Raf-kinases play an important role in stomatal VPD signaling. Moreover, high VPD–induced stomatal closure was impaired in receptor-like pseudokinase GUARD CELL HYDROGEN PEROXIDE-RESISTANT1 (GHR1) mutant alleles. Notably, the classical transient “wrong-way” VPD response was absent in ghr1 mutant alleles. These findings reveal genes and signaling mechanisms in the elusive high VPD–induced stomatal closing response pathway.

Experimental Study on the Heat Transfer Performance of Pump-assisted Capillary Phase-change Loop

To overcome the two-phase flow instability of traditional boiling heat dissipation technologies, a porous wick was used for liquid-vapor isolation, thus realizing efficient and stable boiling heat dissipation. A pump-assisted capillary phase-change loop with methanol as working medium was established to study the effect of liquid-vapor pressure difference and heating power on its start-up and steady-state characteristics. The results indicated that the evaporator undergoes four heat transfer modes including flooded, partial flooded, thin film evaporation and overheating. The thin film evaporation mode was the most efficient one with the shortest start-up period. Besides, the heat transfer modes were determined by liquid-vapor pressure difference and power. The heat transfer coefficient could be significantly improved and the thermal resistance could be reduced by increasing liquid-vapor pressure difference as long as it did not exceed 8 kPa. However, when the liquid-vapor pressure difference exceeded 8kPa, its influence on the heat transfer coefficient weakened. In addition, a two-dimensional heat transfer mode distribution diagram considering both liquid-vapor pressure difference and power was drawn through a great number of experiments. During engineering application, the liquid-vapor pressure difference can be controlled to maintain efficient thin film evaporation in order to achieve the optimum heat dissipation effect.

Potential of sand as a medium of water evaporation – A Review

The purpose of this review is to give an up to date overview of the existing literature on water evaporation from the sand. The paper summarizes the factors influencing evaporation rates in water evaporation from sand such as solar radiation, air temperature, air moisture, the temperature at the water-table, relative humidity of the air, depth of the ground water table, wind speed, vapor pressure difference, sand capillary, hydraulic conductivity and particle size of sand. Limitations and constraints identifying existing gaps are discussed, as well as the potential applicability.