Experimental study on dynamic thermal responses and comfortable evaluations under bathing conditions.

This study investigated the dynamic thermal responses and comfortable boundaries under different bathing conditions through a series of human subject experiments. Eleven subjects' subjective questionnaires and physiological parameters were collected. During the 40-min 40 °C bath, subjects' whole-body thermal sensation, sweating sensation, and fatigue relieving vote increased from 0 (neutral) to 2.6 (near 'hot' sensation), 3.5 (near 'very sweaty' sensation), and 1.6 (near 'relieved' vote), respectively. Thermal comfort vote firstly increased to 1.5 (near 'comfortable' sensation) in the first 10 min, then decreased to -0.5 (between 'neutral and slightly uncomfortable' sensation), and eventually remained around 1.1 ('slightly comfortable' sensation) after the bath. After the 40-min bath, the skin temperature and core temperature rose by 2.0 °C and 0.9 °C respectively. The mean heart rate increased by 45% and blood pressure decreased in most subjects. The percentage of ß brain wave (representing concentration emotion) decreased while that of δ brain wave (representing relaxing emotion) increased, indicating that the bathed subjects tended to be more relaxed and sleeping emotionally. Based on these observations, we inferred that bathing thermal comfort can be influenced by multiple factors simultaneously but effective evaluation tools quantifying bathing thermal comfort are yet to be produced. Compared with showering, bathing usually induces more intensive thermal stress to the body, causing similar changing patterns but stronger amplitudes in subjective and physiological responses. These results can provide references for more comfortable and healthier bathroom environment design and relevant environmental conditioning products.

Review on descaling and anti-scaling technology of heat exchanger in high-salt wastewater thermal desalination.

Thermal desalination evaporation of high-salt wastewater has been widely used in industry because of the proposed concept of 'zero liquid discharge'. However, due to the high content of Ca2+ and Mg2+ in high-salt wastewater, the heat exchanger, as the main treatment equipment, suffers from serious scaling problems. This review presents descaling and scale inhibition technologies of high-salt wastewater. The advantages and disadvantages of various technologies are summarized and analyzed to provide theoretical support for the research of descaling and anti-scaling of heat exchangers with high-salt wastewater. In future industrial development, the synergistic application of electromagnetic water treatment technology and scale inhibitors can significantly improve the anti-scaling effect, which can reach over 95% stably. Furthermore, the addition of a physical field can also expand the application range of scale inhibitors.

High-density thermal sensitivity of the hand under different thermal states and stimulus intensities.

Understanding how the human body senses small-scale heating and cooling stimuli can help researchers evaluate thermal comfort effects and health risks of thermal stimulus combinations under complex thermal exposure. Two experiments measured high-density thermal sensitivity on the hand to investigate whether the initial thermal states and stimulus intensities affect thermal sensitivity. After pilot tests, a 23°C cold-water bath and a 41°C hot-water bath were applied to create initial states deviating from thermal neutrality. The whole hand and part of the wrist with all test spots were immersed for 1 min and dried by a towel. Results showed that cold sensitivity and warmth sensitivity have a linear relationship with each other, but 16 of 20 subjects (80%) were more sensitive to cooling than to heating. The 1-min water-bath treatment significantly reduced hand thermal sensitivity. Compared with a thermally neutral state, a cold-water bath and hot-water bath reduced cold sensitivity by 22% and 61%, respectively, and reduced warmth sensitivity by 47% and 51%, respectively. Under a thermally neutral state, the perceptible thresholds for cooling and heating stimuli were -1.3°C and +1.8°C, respectively. Comfortable stimulating temperature ranges were 24°C-30°C for cooling and 34°C-39°C for heating. Thermal sensitivity differences among stimulus intensities were small, but differences among test spots and subjects were significant.

Overall and thermal comfort under different temperature, noise, and vibration exposures.

Public transports like the bus and subway inherently experience noise, vibration, and temperature variations that are different from building environment. Each of them can influence passengers' comfort, but little is known about their combined effects, especially how they affect thermal comfort. This paper presents experimental results from a series of human subject tests under different noises, vibrations, and temperatures. 32 subjects' subjective perception and physiological response were collected under three temperatures (22.5, 25.5, 28.5℃), five noise levels (55, 60, 65, 70, 75 dB(A)), and five vibrating accelerations (0, 0.2, 0.4, 0.6, 0.8 m/s2 ). We also varied the noise and vibration spectrums to simulate the bus and subway environments. In total, 48 195-min and 192 115-min laboratory tests were conducted. By using significance tests (paired t tests and two-way ANOVA tests) and sensitivity analysis (Treed Gaussian Process), the results show that temperature, noise, and vibration exposures can significantly affect subjects' overall satisfaction. More interestingly, high noise and vibration levels can cause warmer thermal sensations. A change in the noise of 20 dB(A) or vibration of 0.6 m/s2 is equivalent to an ambient temperature change of 0.6 °C. We also observed higher heart rates and metabolic heat production at higher levels of noise and vibrating accelerators. Based on the test results, regression models were developed to describe the combined effects of temperature, noise, and vibration on subjects' overall comfort perception and thermal neutral temperature. They can serve as references for the design and operation of public transport environments.

Techno-economic analysis of residential building heating strategies for cost-effective upgrades in European cities.

The energy crisis in Europe requires cost-effective evaluations of residential heating strategies to reduce costs and mitigate greenhouse gas emissions. This research studied different heating systems in China and Europe. Based on heating energy surveys, simulation models were developed and further expanded for European cities. Monte Carlo analyses were conducted to understand the heating demand and utility costs in Rome, Madrid, and Athens. The sensitivity analysis found that electrifying heating systems with heat pumps can reduce household heating costs and mitigate European cities' dependence on natural gas. However, the high upfront investment may hinder the cost-effective deployment of high-performance heat pump systems. Building envelope retrofits can also provide plausible energy savings despite relatively long payback periods. Financial incentive analyses were conducted to quantify how fiscal measures can improve technologies' techno-economic performance. Finally, the paper provided policy recommendations on future building cost-effective retrofits and heating electrification in Europe.