Thermal balance of greenhouse complexes of the V generation in the summer period

When growing various crops in greenhouses an important condition for obtaining high yields is compliance with the required parameters of the temperature regime of the air environment. The air conditioning systems currently used in greenhouses of the V generation “Ultra Clima” are equipped with adiabatic panels that cool the air entering the room by evaporation of moisture from their surface. However, in some cases, such systems are not able to support the required values. This is due to the large heat flows entering the greenhouse in the summer. The paper analyzes the temperature balance of the air environment of greenhouses of the V generation, evaluates the main heat flows, determines the operating modes of cooling systems that guarantee sufficient cooling capacity to achieve the required temperatures in the room.

Heat and moisture transfer kinetics and temperature during drying of fabrics

The methods of approximation of the curve of the drying rate of fabrics according to the methods of A. V. Lykov and V. V. Krasnikov are described. The results of processing experimental data on convective tissue drying are presented. Equations are given for determining the drying time of fabrics, the density of heat flows and the temperature of fabrics during the drying process. The equations for determining the drying coefficient and the relative drying rate are given. An analytical method for determining the temperature for the period of falling drying rate is considered. The comparison of the temperature values according to the results of analytical solutions with the values obtained by the experimental formula is given. It is shown that the number of Bio during drying of fabrics is less than one, and the main limiting factor is the external heat and moisture exchange of the evaporation surface from the surface of the material with the environment. Verification of the reliability of the calculated values obtained with experimental ones is presented. The discrepancy between the values is within 5 % of the accuracy of the experiment and processing.

A fast thermoelastic model based on the half-space theory applied to elastohydrodynamic lubrication of line contacts involving free boundaries

This study allows contact models based on semi-analytical methods including the impacts of thermoelastic deformations in contacts of finite dimension bodies. The proposed method controls heat flows crossing free boundaries. A comparison with FEA reveals that the proposed method can reduce the calculation times by more than 98%. The paper introduces the thermoelasticity effects into thermal-elastohydrodynamic lubrication (TEHL) modeling of line contact problems. The analysis reveals that including thermoelastic deformations changes the pressure profile and tends to localize the pressure close to the distribution center. Compared to TEHL simulations, the examined configurations caused an overall increase in the maximum pressure by about 9%, an overall film thickness reduction of about 7%, and an overall temperature increase of about 2 K.

Studying the causes of destruction of steam superheater tubes in boiler equipment

Results of comprehensive studies of samples of prematurely destroyed 57×4 mm steam superheaer tubes of STBA 22 steel used in a boiler unit of Singburi Sugar Co, Ltd factory (Thailand) are presented. The tubes were manufactured at Interpipe Niko Tube Ltd. (Ukraine) according to JIS G 3462 Standard (Japan). They were destroyed in a short (~240 hrs) term of operation. The cause of premature destruction of tubes of the above steel grade and size assortment in the boiler unit has been established. Based on present-day investigation methods (metallography, X-ray diffraction, etc.), it was found that the tubes were operated with violation of fuel combustion conditions and heat-carrying agent circulation. Characteristic features of operation of damaged tubes include high thermal stresses from the side of the fire-chamber and limitation (or absence) of circulation of the heat-carrying agent (blockage in bends, drum heads, etc.). During operation, the tubes were also exposed to significant thermal vibration stresses (unstable combustion conditions). Prolonged overheating occurred at temperatures above 1000 °C because of violation of circulation of heat-carrying agent and unstable combustion mode. High thermal stresses at almost complete absence of a heat-carrying agent, uneven distribution of growing heat flows caused by violation of the combustion mode in the fire-chamber contributed to accelerated degradation of structure and thermal destruction of the tube metal. In a short term of operation (~240 hours), there was a significant change in the tube size (accelerated high-temperature creep) and complete recrystallization of metal structure throughout the entire wall thickness of the damaged tubes. It has been established that the accelerated degradation of metal microstructure in the destroyed tubes was associated with both overheating of the tube wall and the as-delivered metal structure non-recommended for operation at high temperatures and pressures. It was shown that it is necessary to adjust the heat treatment conditions for these tubes at Interpipe Niko Tube Ltd. The study results have made it possible to develop recommendations for eliminating violations of operating conditions and establishing control of actual heat flows in the most thermally loaded sections of the Singburi Sugar Co. Ltd factory’s steam boiler superheater. Taking into account peculiarities of the boiler equipment and its operating conditions, it was also recommended to use a more heat-resistant and refractory steel instead of the currently used material for manufacture of the steam superheater tubes. Keywords: boiler tube, steam superheater, damage, thermal destruction, structure degradation, combustion conditions, heat carrier circulation, overheating.

ENERGY SAVING OF MODULAR BUILDINGS WITH THE HELP OF BIOGAS TECHNOLOGIES

Ukraine has significant land resources for agriculture and is able to provide its population not only with food but also with raw materials for bioenergy. The article presents a graph of heat capacities and the distribution of heat flows in a bioreactor. The dependences for determining the heat fluxes of flat and cylindrical surfaces are presented. The article outlines the present state of utilization of fallen leaves of trees. The method of utilization by anaerobic fermentation is proposed. The design of bioreactors and the main factors influencing the methane formation process are considered. The methodology for calculating the biogas production process is presented. The productivity of the bioreactor has been determined, depending on the temperature of the raw material and the time of hydraulic resistance

The qutrit as a heat diode and circulator

We investigate the heat transport properties of a three-level system coupled to three thermal baths, assuming a model based on superconducting circuit implementations. The system-bath coupling is mediated by resonators which serve as frequency filters for the different qutrit transitions. Taking into account the finite quality factors of the resonators, we find thermal rectification and circulation effects not expected in configurations with perfectly-filtered couplings. Heat leakage in off-resonant transitions can be exploited to make the system work as an ideal diode where heat flows in the same direction between two baths irrespective of the sign of the temperature difference, as well as a perfect heat circulator whose state is phase-reversible.

Effect of metal heat guide structure on the performance of planar Si thermoelectric generator embedded in SiO2 inter-layer dielectric

Heat guide (HG) is a layer providing a heat flux to a desired part in micro thermoelectric generator (µ-TEG). In this work, we experimentally investigated the impact of the HG structure on the thermoelectric voltage of a cavity-free planer-type Si-nanowire (Si-NW) µ-TEG, which is embedded in SiO2 acting as an inter-layer dielectric (ILD). Although the heat flows also through the ILD, a sub-µm-thick HG is able to selectively guide the heat flux to hot side terminal of the µ-TEG, and the µ-TEG performance is improved by increasing the thickness of the HG.

Reformulation of elliptic equations for heat transfer and diffusion in solids with space-time algebra

In this paper, we demonstrate the application of non-commutative space-time algebra of sedeons to generalize the system of equations describing heat transfer and impurity diffusion in solids at finite velocity. It is shown that by analogy with electrodynamics, these transfer processes can be described using a compact second-order sedeonic equation for generalized scalar and vector potentials. On the one hand, this equation is reduced to the system of first-order differential equations for vortex-less mass and heat flows, and on the other hand, it can be transformed to the second-order elliptical equations for the profiles of temperature and impurity concentration. The comparison of peculiarities in transfer within the frames of parabolic and elliptic equations is discussed.

Some Studies of the Geology, Volcanic History, and Geothermal Resources of the Okataina Volcanic Centre, Taupo Volcanic Zone, New Zealand

<p>Okataina Volcanic Centre is the most recently active of the four major rhyolite eruptive centres in the Taupo Volcanic Zone of New Zealand. Within the Centre lies Haroharo Caldera, a complex of overlapping collapse structures resulting from successive voluminous pyroclastic eruptions from the same general source area. At least four main and possibly two minor caldera-forming eruptions have occurred during the last 250,000 years, although poor exposure means that attempts to interpret the early structural history are highly speculative. Although there is no compelling evidence of structural updoming within Haroharo Caldera, magma resurgence has followed the last major caldera-forming eruption of the Rotoiti Breccia at [greater than or equal to] 42,000 years B.P. Eruption of this magma within the caldera has formed the two large rhyolite lava and pyroclastic piles of the Haroharo Volcanic Complex and Tarawera Volcanic Complex, plus two subsidiary adjacent complexes at Okareka and Rotoma. All these intracaldera eruptives are younger than 20,000 years B.P., with the most recent eruptions from Tarawera; of rhyolite at c. 700 years B.P., and of basalt in 1886 A.D. A considerable amount of earlier work carried out at Okataina was directed mainly at petrology and chemistry of the rhyolites forming the Tarawera and Haroharo Volcanic Complexes. The present study has arisen from a 1:50,000 mapping programme at Okataina and has sought to examine structures and volcanic history in greater detail, and to consider the resulting geological implications for geothermal resources. Caldera boundaries have been mapped, and two major vent lineations are defined, apparently related to fundamental basement fractures which have controlled location of the Tarawera and Haroharo Volcanic Complexes. An intracaldera ring fault is also suggested by the sub-circular arrangement of some young volcanic vents. The Haroharo and Tarawera Complexes are mapped, with locations of source vents, and dating of the major lavas and pyroclastic deposits. All the post-20,000 year eruptives are placed in four main emptive episodes at Haroharo, and five at Tarawera. The near-source pyroclastic surge and flow deposits are 14C dated, and with their associated widespread plinian fall deposits they provide time planes for dating the associated lavas. The emptive episodes generally appear to have been of much shorter duration than the intervening quiescent periods which lasted for thousands of years. All the eruptive episodes at Haroharo involved multiple eruptions from vents spread out over several kilometres along the vent lineations. Similar multiple vent eruptions can be demonstrated for some of the Tarawera eruptive episodes. More than 500 km3 of magma has been erupted from Haroharo Caldera during the last 250,000 years, 80 km3 of which was erupted in the Last 20,000 years. This history suggests that a large magmatic heat source should continue to underlie the Okataina Volcanic Centre. However, very little surface hydrothermal activity occurs within Haroharo Caldera. It is suggested that the large external hydrothermal fields at Tikitere, Waimangu-Waiotapu-Waikite, and possibly Kawerau, are related to Haroharo Caldera heat sources. Presently available data are summarized for hydrothermal fields in and adjacent to Haroharo Caldera, and new analyses are presented for some warm springs discovered within the caldera. Estimates and measurements of chloride fluxes in lakes and rivers are reported. The chloride flux values suggest the occurrence of larger hydrothermal heat flows into lakes and rivers than are apparent at the surface. Measurements of chloride flux in the Tarawera River showed that 280 g s-1 of chloride is added to the river within Haroharo Caldera below the Lake Tarawera outlet. Only 80 g s-1 of this chloride comes from known geothermal sources. A total chloride flux of 760 g s-1 in the Tarawera River passing out of the Okataina Volcanic Centre indicates a minimum geothermal heat flow of 600 MW. Estimates of heat flows in other drainage paths from Haroharo Caldera suggest that minimum total heat flow from the caldera may exceed 1500 MW. A large heat flow from the caldera would appear consistent with the volcanic history. Some suggestions are made for further investigation of the geothermal resources</p>

Some Studies of the Geology, Volcanic History, and Geothermal Resources of the Okataina Volcanic Centre, Taupo Volcanic Zone, New Zealand

<p>Okataina Volcanic Centre is the most recently active of the four major rhyolite eruptive centres in the Taupo Volcanic Zone of New Zealand. Within the Centre lies Haroharo Caldera, a complex of overlapping collapse structures resulting from successive voluminous pyroclastic eruptions from the same general source area. At least four main and possibly two minor caldera-forming eruptions have occurred during the last 250,000 years, although poor exposure means that attempts to interpret the early structural history are highly speculative. Although there is no compelling evidence of structural updoming within Haroharo Caldera, magma resurgence has followed the last major caldera-forming eruption of the Rotoiti Breccia at [greater than or equal to] 42,000 years B.P. Eruption of this magma within the caldera has formed the two large rhyolite lava and pyroclastic piles of the Haroharo Volcanic Complex and Tarawera Volcanic Complex, plus two subsidiary adjacent complexes at Okareka and Rotoma. All these intracaldera eruptives are younger than 20,000 years B.P., with the most recent eruptions from Tarawera; of rhyolite at c. 700 years B.P., and of basalt in 1886 A.D. A considerable amount of earlier work carried out at Okataina was directed mainly at petrology and chemistry of the rhyolites forming the Tarawera and Haroharo Volcanic Complexes. The present study has arisen from a 1:50,000 mapping programme at Okataina and has sought to examine structures and volcanic history in greater detail, and to consider the resulting geological implications for geothermal resources. Caldera boundaries have been mapped, and two major vent lineations are defined, apparently related to fundamental basement fractures which have controlled location of the Tarawera and Haroharo Volcanic Complexes. An intracaldera ring fault is also suggested by the sub-circular arrangement of some young volcanic vents. The Haroharo and Tarawera Complexes are mapped, with locations of source vents, and dating of the major lavas and pyroclastic deposits. All the post-20,000 year eruptives are placed in four main emptive episodes at Haroharo, and five at Tarawera. The near-source pyroclastic surge and flow deposits are 14C dated, and with their associated widespread plinian fall deposits they provide time planes for dating the associated lavas. The emptive episodes generally appear to have been of much shorter duration than the intervening quiescent periods which lasted for thousands of years. All the eruptive episodes at Haroharo involved multiple eruptions from vents spread out over several kilometres along the vent lineations. Similar multiple vent eruptions can be demonstrated for some of the Tarawera eruptive episodes. More than 500 km3 of magma has been erupted from Haroharo Caldera during the last 250,000 years, 80 km3 of which was erupted in the Last 20,000 years. This history suggests that a large magmatic heat source should continue to underlie the Okataina Volcanic Centre. However, very little surface hydrothermal activity occurs within Haroharo Caldera. It is suggested that the large external hydrothermal fields at Tikitere, Waimangu-Waiotapu-Waikite, and possibly Kawerau, are related to Haroharo Caldera heat sources. Presently available data are summarized for hydrothermal fields in and adjacent to Haroharo Caldera, and new analyses are presented for some warm springs discovered within the caldera. Estimates and measurements of chloride fluxes in lakes and rivers are reported. The chloride flux values suggest the occurrence of larger hydrothermal heat flows into lakes and rivers than are apparent at the surface. Measurements of chloride flux in the Tarawera River showed that 280 g s-1 of chloride is added to the river within Haroharo Caldera below the Lake Tarawera outlet. Only 80 g s-1 of this chloride comes from known geothermal sources. A total chloride flux of 760 g s-1 in the Tarawera River passing out of the Okataina Volcanic Centre indicates a minimum geothermal heat flow of 600 MW. Estimates of heat flows in other drainage paths from Haroharo Caldera suggest that minimum total heat flow from the caldera may exceed 1500 MW. A large heat flow from the caldera would appear consistent with the volcanic history. Some suggestions are made for further investigation of the geothermal resources</p>