Design solutions for gravity-independent heat pipes

Heat pipes with mesh wicks were designed (working liquid – water, envelope – copper tube). Wicks from the mesh of various weaves (plain, twill, leno and looped) with improved hydrophilic properties and secondary capillary structure were developed. Heat pipes are gravity-independent, adapted to work in various conditions of orientation and localization, and provide the transfer of high heat flux powers (up to 25 W/cm2 ). The peculiar properties of the developed heat pipes in contrast to the traditional heat pipes (with powder wicks) are: high performance characteristics, resistance to deep freezing; vibrostability.

Thermodynamic Features and Design of Solar-Air Source Composite Heating System

Facing the huge energy consumption of buildings, it is highly practical to study every aspect of energy-saving technologies for heating and cooling devices. Solar thermal technology and air/water source heat pump are two popular energy-saving technologies, which could be combined into a composite heating system with good energy-saving effect and efficiency. This paper constructs a solar-air source composite heating system, analyzes its thermodynamic features, and builds up the corresponding thermodynamic model. In addition, the authors modeled the daytime and nighttime heat balances, as well as the monthly cumulative heat supply for the constructed system. Finally, a dual-tank composite heating system was designed with independent heat supply/storage. The proposed models and system were proved valid and scientific through experiments.

Concurrent Heat and Intermittent Hypoxic Training: No Additional Performance Benefit Over Temperate Training

Purpose: To examine whether concurrent heat and intermittent hypoxic training can improve endurance performance and physiological responses relative to independent heat or temperate interval training. Methods: Well-trained male cyclists (N = 29) completed 3 weeks of moderate- to high-intensity interval training (4 × 60 min·wk−1) in 1 of 3 conditions: (1) heat (HOT: 32°C, 50% relative humidity, 20.8% fraction of inspired oxygen, (2) heat + hypoxia (H+H: 32°C, 50% relative humidity, 16.2% fraction of inspired oxygen), or (3) temperate environment (CONT: 22°C, 50% relative humidity, 20.8% fraction of inspired oxygen). Performance 20-km time trials (TTs) were conducted in both temperate (TTtemperate) and assigned condition (TTenvironment) before (base), immediately after (mid), and after a 3-week taper (end). Measures of hemoglobin mass, plasma volume, and blood volume were also assessed. Results: There was improved 20-km TT performance to a similar extent across all groups in both TTtemperate (mean ±90% confidence interval HOT, −2.8% ±1.8%; H+H, −2.0% ±1.5%; CONT, −2.0% ±1.8%) and TTenvironment (HOT, −3.3% ±1.7%; H+H, −3.1% ±1.6%; CONT, −3.2% ±1.1%). Plasma volume (HOT, 3.8% ±4.7%; H+H, 3.3% ±4.7%) and blood volume (HOT, 3.0% ±4.1%; H+H, 4.6% ±3.9%) were both increased at mid in HOT and H+H over CONT. Increased hemoglobin mass was observed in H+H only (3.0% ±1.8%). Conclusion: Three weeks of interval training in heat, concurrent heat and hypoxia, or temperate environments improve 20-km TT performance to the same extent. Despite indications of physiological adaptations, the addition of independent heat or concurrent heat and hypoxia provided no greater performance benefits in a temperate environment than temperate training alone.

Impaired Heat Adaptation From Combined Heat Training and “Live High, Train Low” Hypoxia

Purpose: To determine whether combining training in heat with “Live High, Train Low” hypoxia (LHTL) further improves thermoregulatory and cardiovascular responses to a heat-tolerance test compared with independent heat training. Methods: A total of 25 trained runners (peak oxygen uptake = 64.1 [8.0] mL·min−1·kg−1) completed 3-wk training in 1 of 3 conditions: (1) heat training combined with “LHTL” hypoxia (H+H; FiO2 = 14.4% [3000 m], 13 h·d−1; train at <600 m, 33°C, 55% relative humidity [RH]), (2) heat training (HOT; live and train <600 m, 33°C, 55% RH), and (3) temperate training (CONT; live and train <600 m, 13°C, 55% RH). Heat adaptations were determined from a 45-min heat-response test (33°C, 55% RH, 65% velocity corresponding to the peak oxygen uptake) at baseline and immediately and 1 and 3 wk postexposure (baseline, post, 1 wkP, and 3 wkP, respectively). Core temperature, heart rate, sweat rate, sodium concentration, plasma volume, and perceptual responses were analyzed using magnitude-based inferences. Results: Submaximal heart rate (effect size [ES] = −0.60 [−0.89; −0.32]) and core temperature (ES = −0.55 [−0.99; −0.10]) were reduced in HOT until 1 wkP. Sweat rate (ES = 0.36 [0.12; 0.59]) and sweat sodium concentration (ES = −0.82 [−1.48; −0.16]) were, respectively, increased and decreased until 3 wkP in HOT. Submaximal heart rate (ES = −0.38 [−0.85; 0.08]) was likely reduced in H+H at 3 wkP, whereas CONT had unclear physiological changes. Perceived exertion and thermal sensation were reduced across all groups. Conclusions: Despite greater physiological stress from combined heat training and “LHTL” hypoxia, thermoregulatory adaptations are limited in comparison with independent heat training. The combined stimuli provide no additional physiological benefit during exercise in hot environments.

ANALYSIS OF THE POSSIBILITIES FOR SAVING AND DEVELOPMENT OF DISTRICT HEATING SYSTEMS ІN UKRAINE

Purpose of the paper is to analyze the main causes leading to the destruction of DH systems in Ukraine, as well as the search for ways to modernize the existing worn-out DH system. After comparison of DH and individual systems, it was concluded that in order to retain the leading positions, the DH should generate heat significantly (by 20-40%) cheaper than individual systems. Several technical measures have been examined in detail and evaluated, namely: transition to cheaper fuels, in particular biomass; transition to technologies that are more efficient for generation of thermal energy (CHP, cogeneration plants, condensing economizers). In addition, it is necessary to create conditions for full-fledged competitiveness of Communal Utilities with independent heat producers, in particular, a simplification of networks connection procedure. No special requirements should be put other than heat carrier parameters and lower heat price. A reliable parallel operation of Communal Utilities and independent companies is possible in DH systems exceeding 50 Gcal / h. The emerged competition must induce Communal Utilities to use biomass on their own CHPs and boilers and produce cheaper heat. An important organizational measure is a full transition from the "cost +" principle in tariff formation to incentive tariff formation. It is also necessary to determine tariff costs separately by each type of licensed activity (production, transportation and supply of heat energy), while not allowing cross subsidies. Summing up the above suggestions it is concluded that state authorities should adopt program documents with strategic direction for the preservation and development of the DH systems.