Solid-state cooling by elastocaloric polymer with uniform chain-lengths

Although the elastocaloric effect was found in natural rubber as early as 160 years ago, commercial elastocaloric refrigeration based on polymer elastomers has stagnated owing to their deficient elastocaloric effects and large extension ratios. Herein, we demonstrate that polymer elastomers with uniform molecular chain-lengths exhibit enormous elastocaloric effects through reversible conformational changes. An adiabatic temperature change of −15.3 K and an isothermal entropy change of 145 J kg−1 K−1, obtained from poly(styrene-b-ethylene-co-butylene-b-styrene) near room temperature, exceed those of previously reported elastocaloric polymers. A rotary-motion cooling device is tailored to high-strains characteristics of rubbers, which effectively discharges the cooling energy of polymer elastomers. Our work provides a strategy for the enhancement of elastocaloric effects and could promote the commercialization of solid-state cooling devices based on polymer elastomers.

Design of a Scalable, Flexible, and Durable Thermoelectric Cooling Device for Soft Electronics Using Kirigami Cut Patterns

A flexible, soft thermoelectric cooling device is presented that shows potential for human cooling applications in wearable technologies and close-to-body applications. Current developments lack integration feasibility due to non-scalable assembly procedures and unsuitable materials for comfortable and durable integration into products. Our devices have been created and tested around the need to conform to the human body which we have quantified through the creation of a repeatable drape testing procedure, a metric used in the textile industry. Inspired by mass manufacturing constraints, our flexible thermoelectric devices are created using commercially available materials and scalable processing techniques. Thermoelectric legs are embedded in a foam substrate to provide flexibility, while Kirigami-inspired cuts are patterned on the foam to provide the drape necessary for mimicking the performance of textile and close to body materials. In total, nine different configurations, three different fill factors and three different Kirigami cut patterns were fabricated and inspected for thermal characterization, mechanical testing, flexibility and drape. Our studies show that adding Kirigami patterns can increase the durability of the device, improve the flexibility, decrease the drape coefficient, and have <1% of impact on cooling performance at higher fill factors (>1.5%), reaching temperature differences up to 4.39 ± 0.17°C between the hot and cold faces of the device. These thermoelectric cooling devices show great flexibility, durability, and cooling for integration into soft cooling products.

Predictive control of the starting pressure of the main oil pipeline

The article calculates the starting pressures and the time of safe shutdown of the pipeline during the transportation of high-viscosity and high pour point oils, the rheological properties of which depend on temperature. When the oil temperature decreases, its viscosity increases and paraffins are released, forming a strong structure, for which additional stress is necessary to shift. To start a stopped oil pipeline transporting oil with such characteristics, the pressure developed by the pumps may not be enough. In this regard, it is necessary to determine the safe time of stopping the oil pipeline. The relevance increases with an increase in the share of high-viscosity and high pour point oil in the total production volume. Predictive control, based on the analysis of data on the characteristics of the transported product and forecasting the nature of their changes, is an intelligent tool for managing the efficiency of technological transport enterprises. Predictive control allows you to choose the optimal way to ensure reliable and trouble-free operation of the main equipment of hydrocarbon transport systems.A numerical experiment was carried out for the effect of seasonal cooling devices to protect permafrost soils from thawing, at the time of a safe shutdown of the oil pipeline. The values of starting pressures have been determined. Dependence of the pressures on the duration of the safe shutdown of the pipeline has been established. It was revealed that due to the operation of seasonally operating cooling devices, the difference between the temperature soil and oil increases during cooling, and the cooling rate increases. More pressure will be required to launch such an oil pipeline.

Optimal ferrofluids for magnetic cooling devices

Superior passive cooling technologies are urgently required to tackle device overheating, consequent performance degradation, and service life reduction. Magnetic cooling, governed by the thermomagnetic convection of a ferrofluid, is a promising emerging passive heat transfer technology to meet these challenges. Hence, we studied the performance metrics, non-dimensional parameters, and thermomagnetic cooling performance of various ferrite and metal-based ferrofluids. The magnetic pressure, friction factor, power transfer, and exergy loss were determined to predict the performance of such cooling devices. We also investigated the significance of the magnetic properties of the nanoparticles used in the ferrofluid on cooling performance. γ-Fe2O3, Fe3O4, and CoFe2O4 nanoparticles exhibited superior cooling performance among ferrite-based ferrofluids. FeCo nanoparticles had the best cooling performance for the case of metallic ferrofluids. The saturation magnetization of the magnetic nanoparticles is found to be a significant parameter to enhance heat transfer and heat load cooling. These results can be used to select the optimum magnetic nanoparticle-based ferrofluid for a specific magnetic cooling device application.

Air-conditioning and the adaptation cooling deficit in emerging economies

Increasing temperatures will make space cooling a necessity for maintain comfort and protecting human health, and rising income levels will allow more people to purchase and run air conditioners. Here we show that, in Brazil, India, Indonesia, and Mexico income and humidity-adjusted temperature are common determinants for adopting air-conditioning, but their relative contribution varies in relation to household characteristics. Adoption rates are higher among households living in higher quality dwellings in urban areas, and among those with higher levels of education. Air-conditioning is unevenly distributed across income levels, making evident the existence of a disparity in access to cooling devices. Although the adoption of air-conditioning could increase between twofold and sixteen-fold by 2040, from 64 to 100 million families with access to electricity will not be able to adequately satisfy their demand for thermal comfort. The need to sustain electricity expenditure in response to higher temperatures can also create unequal opportunities to adapt.

Thermographical study of geometry and phase change influence on PDMS Microchannel liquid cooling devices

This work proposes a methodology in which high speed camera imaging is combined with infrared (IR) thermography to look at the effect of geometric parameters and boiling in the effectiveness of these coolers. PDMS microchannels were manufactured with 3 channel widths: 250, 500 and 750µm. HFE7100 was used as the refrigerant. Pressure losses were significant for the thinnest geometry as clogging and flow reversal were observed. The dissipated heat flux, as measured by the IR camera was higher in the largest channels, due to the PDMS poor conductivity. Results obtained with HFE7100 were then compared with those obtained with water at single-phase flow. For the same geometry, HFE 7100 resulted in a higher heat transfer coefficient than water.

Experimental Investigation of Boiling Heat Transfer in a Liquid Chamber With Partially Soluble Nanofluids

Boiling heat transfer (BHT) is a promising technique to remove a high heat flux emitted from next-generation electronic devices. However, critical heat flux (CHF) is a big problem in BHT because it restricts the maximum performance of the cooling devices using BHT. Nanofluid has been widely used to improve the CHF. In this study, the authors investigated the BHT of a compact cooling device at low pressure using a special nanofluid: that is made with partially soluble particles in water. The experimental result found that the CHF with the special nanofluid is 170 W/cm2 and is higher than that with nanofluid made with an insoluble nanoparticle.

Contact Angle Tuning of Copper Microporous Structures

Two-phase, capillary-fed cooling devices are appealing thermal management technologies due to their potential for high heat transfer performance and ease of system-level integration. While existing evaporative wicking structures such as copper inverse opals (CIOs) and copper wire meshes (CWMs) have shown promise for achieving target heat dissipation rates of 100 Wcm−2 or greater, the reliability of these structures for long-term device operation and optimal capillary-driven boiling performance has not received much attention. To ensure proper functionality of the evaporator wick, the microporous copper structures must retain a hydrophilic contact angle during device operation. Surface oxidation of the copper is a critical degradation mechanism that must be addressed to preserve the integrity of the wick. In this study, we systematically investigate the contact angle change of untreated copper and various copper oxides under different conditions. To avoid the formation of hydrophobic Cu2O, we pre-oxidize the copper micro porous wick to form hydrophilic cupric oxide CuO and study the effect of various thermal and chemical oxidation recipes on the hydrophilicity and morphology of the resulting structures. A chemical oxidation formula is implemented for the creation of a stable superhydrophilic surface at a low temperature (70°C) for copper inverse opals (CIOs) (5 μm pore size) and copper wire meshes (CWMs) (76 μm pore opening). The recipe has been optimized to create nano CuO needles with a length of &lt; 100 nm and keep the necks (∼1 μm diameter) open for better capillary wicking of the working fluid. The findings of this study potentially benefit the development of copper-based capillary-fed cooling devices.

Perches as Cooling Devices for Reducing Heat Stress in Caged Laying Hens: A Review

Heat stress is one of the most detrimental environmental challenges affecting the biological process and the related production performance of farm animals, especially in poultry. Commercial laying hens have been bred (selected) for high egg production, resulting in increased sensitivity to heat stress due to breeding-linked metabolic heat production. In addition, laying hens are prone to heat stress due to their inadequate species-specific cooling mechanisms resulting in low heat tolerance. In addition, hens have no sweat glands and feathering covers almost their entire body to minimize body heat loss. The poultry industry and scientists are developing cooling methods to prevent or reduce heat stress-caused damage to chicken health, welfare, and economic losses. We have designed and tested a cooling system using perches, in which chilled water (10 °C) circulates through a conventional perch passing through the layer cages to offer the cooling potential to improve hen health, welfare, and performance during acute and chronic periods of heat stress (35 °C). This review summarizes the outcomes of a multi-year study using the designed cooled perch system. The results indicate that conducting heat from perching hens directly onto the cooled perch system efficiently reduces heat stress and related damage in laying hens. It provides a novel strategy: perches, one key furnishment in cage-free and enriched colony facilities, could be modified as cooling devices to improve thermal comfort for hens during hot seasons, especially in the tropical and subtropical regions.

Comparative analysis of technologies for cleaning finned bimetallic pipes of air cooling devices and methods for controlling contamination of the surface of aluminum alloys

The results of the analysis of existing cleaning technologies for finned bimetallic pipes and methods for monitoring the contamination of the surface of aluminum alloys are presented and their disadvantages are established. It is shown that the technology used for cleaning pipes obtained by cold deformation is energy-consuming, ineffective and laborious, and the existing methods of contamination control do not provide a quantitative express assessment of the surface to be cleaned. Keywords: finning surface, contamination, cleaning, alkaline solution, finned bimetallic pipes, air cooler, control. [email protected]