The Solving of the Inverse Thermal Conductivity Problem for Study the Short Linear Heat Pipes

The results of studies by solving the inverse thermal conductivity problem of the heat capacity of evaporator of the short linear heat pipes (HP’s) with a Laval nozzle-liked vapour channel and intended for cooling spacecraft and satellites with strict take-off mass regulation are presented. Mathematical formulation of the inverse problem for the HP’s thermal conductivity in one-dimensional coordinate system is accompanied by the measurement results using the monotonic heating method in a vacuum adiabatic calorimeter the HP’s surface temperatures along the longitudinal axis over the entire temperature load range, thermal resistance, and arrays of thermal power data on the evaporator Qev and vortex flow calorimeter Qcond for the condensation surface allow us to estimate the average value of the evaporator heat capacity Cev by solving the inverse thermal conductivity problem in the HP’s evaporator region. Since at the beginning of working fluid boiling for a certain time interval, the temperature of the capillary-porous evaporator remains close to constant, and with the continuation of heating and by solving the inverse thermal conductivity problem, it becomes possible to calculate the heat capacity of the working evaporator and the evaporation specific heat of the boiling working fluid and compare it with the table values.

Annual and seasonal changes of the air temperature with altitude in the Upper Dades valley, High Atlas, Morocco

The purpose of this study is to determine the size of air temperature changes with altitude in the mountains of the arid zone, on the example of the Upper Dades valley(High Atlas, Morocco). The air temperature change with altitude was determined on the basis of 5 years data from three meteorological stations. The analysis was carried out on an annual and seasonal basis. The annual and daily variations of thermal gradients between pairs of stations were also determined. It was found that the average thermal gradient in the Upper Dades valley was-1.02℃ per 100 m. The highest values of the thermal gradient occur in winter and the lowest in summer. In winter,the thermal gradient was characterized by the greatest variability. Minima of the daily variation of air temperature gradients were observed in early morning hours and maxima around midday. In the lower part of the valley, air temperature inversion frequently developed between 10 AM and 3 PM UTC.The obtained results show high thermal gradients in the mountains of the arid zone, with their annual amplitude increasing in the lower parts of the valley.The instantaneous values of the gradients were significantly modified by the supply of latent heat and the occurrence of dust storms. It has been shown that the advection factor plays an important role in shaping large gradient values. The study contains novel results of thermal gradient measurements in high mountains of arid zone.

A selective reflecting film with a temperature-dependent pitch length

A(polymer network/liquid crystal/chiral dopants) composite exhibiting a temperature-sensing switch of infrared spectrum has been developed.Because of the different change of the chiral dopant in the helical twisting power and the anchoring effect of the polymer network,the polymer stabilized liquid crystal(PSLC) films,of which the bandwidth of the selective reflection spectra increased with changing temperature,were obtained.

Characteristics of Boundary Layer Structure during a Persistent Haze Event in the Central Liaoning City Cluster, Northeast China

The characteristics of boundary layer structure during a persistent regional haze event over the central Liaoning city cluster of Northeast China from 16 to 21 December 2016 were investigated based on the measurements of particulate matter（PM） concentration and the meteorological data within the atmospheric boundary layer（ABL）. During the observational period, the maximum hourly mean PM_（2.5） and PM10 concentrations in Shenyang, Anshan, Fushun, and Benxi ranged from 276 to 355 μg m–3 and from 378 to 442 μg m–3, respectively, and the lowest hourly mean atmospheric visibility（VIS） in different cities ranged from 0.14 to 0.64 km. The central Liaoning city cluster was located in the front of a slowly moving high pressure and was mainly controlled by southerly winds. Wind speed（WS） within the ABL（〈 2 km） decreased significantly and WS at 10-m height mostly remained below 2 m s–1 during the hazy episodes, which was favorable for the accumulation of air pollutants. A potential temperature inversion layer existed throughout the entire ABL during the earlier hazy episode [from 0500 Local Time（LT） 18 December to 1100 LT 19 December], and then a potential temperature inversion layer developed with the bottom gradually decreased from 900 m to 300 m. Such a stable atmospheric stratification further weakened pollutant dispersion. The atmospheric boundary layer height（ABLH） estimated based on potential temperature profiles was mostly lower than 400 m and varied oppositely with PM_（2.5） in Shenyang. In summary, weak winds due to calm synoptic conditions, strong thermal inversion layer, and shallow atmospheric boundary layer contributed to the formation and development of this haze event.The backward trajectory analysis revealed the sources of air masses and explained the different characteristics of the haze episodes in the four cities.

Optimal flight parameters of unmanned helicopter for tea plantation frost protection

To determine proper flight parameters of an unmanned helicopter for tea plantation frost protection,field experiments were conducted to study the impact of flight height,speed and interval on airflow disturbance and temperature rise around tea canopies based on the analysis and simulation of frost protection with a certain helicopter.The relationship between temperature rise after flight and the above flight parameters was established through a regression orthogonal experiment,based on which the optimal combination of flight parameters was obtained through the single-factor golden section method.The results showed that wind speed around tea canopies decreased with the increase of flight height when flight speed was constant.There was a multivariate linear relationship between temperature rise and flight parameters,and the sequence of flight parameters’influence on frost protection effect was flight interval,flight height,flight speed.The optimal combination of flight parameters were flight height of 4.0 m,flight speed of 6.0 m/s and flight interval of 20 min.After the flight with the above parameters air temperature around tea canopies increased 1.6℃ when background thermal inversion strength was 3.8℃.

Review of air disturbance technology for plant frost protection

Confronted with severe frost damage to plants,methods,technologies and equipment have been developed and applied during the past century.The paper presents a comprehensive review on the most effective and active technology to protect plants from radiation frost based on air disturbance technology.The working principle of the technology was elaborated with frost protection mechanism,structures and applicability of three types of working patterns:conventional wind machines,selective inverted sink and portable vertical blowing.As an automatic mechanized technology,control strategy,applicable occasion and proper parameters are introduced for each type of working pattern.The operation of the technology and equipment depends on plant critical temperature,prevailing climatic conditions,thermal inversions strength,as well as costs.The frost protection performance and effectiveness of conventional horizontal wind machines,selective inverted sinks and helicopters are discussed and compared from the cost-effectiveness and application aspects,and the feasibility of selective inverted sinks is still controversial.Therefore,conventional wind machines are the best choice for plant frost protection and consequently are widely used in temperate and subtropical areas throughout the world.The frost protection application with helicopters is not easy to use during the frost nights with high cost.The paper also provides researchers with some perspectives on improving air disturbance technology and its equipment,and some practice recommendations for growers.

Comparative experiments and effectiveness evaluation on vertical blowing fans(VBF)for frost protection

Experiments were conducted to evaluate the performance of vertical blowing fans(VBF)for frost protection in a vineyard on a steep slope near Napa Valley in Northern California,USA,and a tea plantation located on undulating terrain in Zhenjiang,China.Minimum temperature comparisons from within the grape vineyard on nights with and without VBF operation with control station minimum temperatures exhibited no temperature benefit.Profile measurements from the test in China indicated that there was an increase in temperature when the VBF was first started,but that benefit was lost over time.No clear benefit from using the VBF was observed.Observation of frost deposition and thermal imagery also showed no benefit except for within about 5 m of the VBF.Based on this work,the effectiveness of the VBF for frost protection was not validated.