Heat transfer plays a crucial role in modern engineering and energy conversion efficiency. Understanding its mechanisms is essential for sustainable energy management. Waste heat recovery, an ...increasingly popular strategy, reduces energy consumption and promotes sustainability. This reprint highlights advancements in heat transfer technology and heat recovery systems, addressing the persistent demand for innovative solutions. The content focuses on four main categories: heat transfer and heat exchangers, heat recovery, renewables, and domestic hot water preparation systems.
Recent progress of including lake subroutines in numerical weather prediction (NWP) models has led to more accurate forecasts. In lake models, one essential parameter is water clarity, parameterized ...via the light extinction coefficient, Kd, for which a global constant value is usually used. We used direct eddy covariance fluxes and basic meteorological measurements coupled with lake water temperature and clarity measurements from a boreal lake to estimate the performance of two lake models, LAKE and FLake. These models represent two 1‐D modeling frameworks broadly used in NWP. The results show that the lake models are very sensitive to changes in Kd when it is lower than 0.5 m−1. The progress of thermal stratification depended strongly on Kd. In dark‐water simulations the mixed layer was shallower, longwave and turbulent heat losses higher, and therefore the average water column temperatures lower than in clear‐water simulations. Thus, changes in water clarity can also affect the onset of ice cover. The more complex LAKE modeled the seasonal thermocline deepening, whereas it remained virtually constant during summer in the FLake model. Both models overestimated the surface water temperatures by about 1°C and latent heat flux by >30%, but the variations in heat storage and sensible heat flux were adequately simulated. Our results suggest that, at least for humic lakes, a lake‐specific, but not time‐depending, constant value for Kd can be used and that a global mapping of Kd would be most beneficial in regions with relatively clear lakes, e.g., in lakes at high altitudes.
Key Points
Time‐independent constant for water clarity can be used for humic lake modeling
The surface temperature response to water clarity changes sign during overturn
Freeze over probably occurs earlier if the lake water clarity decreases
The synergistic effect of urban heat island (UHI) and urban moisture island (UMI) aggravates the heat stress during hot summers. To investigate the mechanisms of UHI and UMI, we developed an advanced ...urban canopy model with more robust predictability of the urban surface heat and moisture budgets by considering dynamic building-tree-air interactions within an enhanced aerodynamic resistance network. Our results show that in a compact high-rise city, anthropogenic heat (AH) emission from building cooling systems is nonnegligible (up to 400 W/m2, including ~60% sensible heat flux and ~40% latent heat flux), which can further aggravate UHI and UMI with a 1.64 °C increase in air temperature and a 0.89 g/kg increase in air specific humidity, respectively. On the other hand, the impact of building-tree-air interactions on UHI and UMI within compact high-rise street canyons is complicated due to strong shading effect and hindered turbulent transport. In general, planting trees effectively reduces UHI (−2.90–0 °C) but leads to increased UMI (+0–1.66 g/kg), therefore an optimized tree planting strategy is needed to avoid heat stress aggravation due to high humidity. Specifically, tall trees with large and small crown areas are optimal tree types for street canyons with low and high aspect ratios, respectively. In addition to city greening, optimal building air-conditioning (AC) control in an energy-efficient mode can reduce outdoor maximum heat stress index by 1.10 °C. Furthermore, synergistic effects of optimal AC operation and optimal tree planting can effectively reduce pedestrians’ dangerous hours with heatstroke risks by 11%–35%.
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•We propose an advanced urban canopy model considering dynamic building-tree-air interactions.•Anthropogenic emissions from buildings aggravate UHI and UMI in compact high-rise cities.•Crudely planted trees may aggravate UHI and UMI in compact high-rise cities.•Two mitigation strategies are proposed, including optimal AC control and optimal tree planting.
A new global estimate of surface turbulent fluxes, latent heat flux (LE) and sensible heat flux (H), and gross primary production (GPP) is developed using a machine learning approach informed by ...novel remotely sensed Solar-Induced Fluorescence (SIF) and other radiative and meteorological variables. This is the first study to jointly retrieve LE, H and GPP using SIF observations. The approach uses an artificial neural network (ANN) with a target dataset generated from three independent data sources, weighted based on triple collocation (TC) algorithm. The new retrieval, named Water, Energy, and Carbon with Artificial Neural Networks (WECANN), provides estimates of LE, H and GPP from 2007 to 2015 at 1° × 1° spatial resolution and on monthly time resolution. The quality of ANN training is assessed using the target data, and the WECANN retrievals are evaluated using eddy covariance tower estimates from FLUXNET network across various climates and conditions. When compared to eddy covariance estimates, WECANN typically outperforms other products, particularly for sensible and latent heat fluxes. Analysing WECANN retrievals across three extreme drought and heatwave events demonstrates the capability of the retrievals in capturing the extent of these events. Uncertainty estimates of the retrievals are analysed and the inter-annual variability in average global and regional fluxes show the impact of distinct climatic events - such as the 2015 El Niño - on surface turbulent fluxes and GPP.
Summary
Crop yield has been greatly enhanced during the last century. However, most elite cultivars are adapted to temperate climates and are not well suited to more stressful conditions. In the ...context of climate change, stress resistance is a major concern. To overcome these difficulties, scientists may help breeders by providing genetic markers associated with stress resistance. However, multistress resistance cannot be obtained from the simple addition of single stress resistance traits. In the field, stresses are unpredictable and several may occur at once. Consequently, the use of single stress resistance traits is often inadequate. Although it has been historically linked with the heat stress response, the heat‐shock protein (HSP)/chaperone network is a major component of multiple stress responses. Among the HSP/chaperone ‘client proteins’, many are primary metabolism enzymes and signal transduction components with essential roles for the proper functioning of a cell. HSPs/chaperones are controlled by the action of diverse heat‐shock factors, which are recruited under stress conditions. In this review, we give an overview of the regulation of the HSP/chaperone network with a focus on Arabidopsis thaliana. We illustrate the role of HSPs/chaperones in regulating diverse signalling pathways and discuss several basic principles that should be considered for engineering multiple stress resistance in crops through the HSP/chaperone network.
The long noncoding RNA (lncRNA) NEAT1 (nuclear enriched abundant transcript 1) is the architectural component of nuclear paraspeckles, and it has recently gained considerable attention as it is ...abnormally expressed in pathological conditions such as cancer and neurodegenerative diseases. NEAT1 and paraspeckle formation are increased in cells upon exposure to a variety of environmental stressors and believed to play an important role in cell survival. The present study was undertaken to further investigate the role of NEAT1 in cellular stress response pathways. We show that NEAT1 is a novel target gene of heat shock transcription factor 1 (HSF1) and is up-regulated when the heat shock response pathway is activated by sulforaphane (SFN) or elevated temperature. HSF1 binds specifically to a newly identified conserved heat shock element in the NEAT1 promoter. In line with this, SFN induced the formation of NEAT1-containing paraspeckles via an HSF1-dependent mechanism. HSF1 plays a key role in the cellular response to proteotoxic stress by promoting the expression of a series of genes, including those encoding molecular chaperones. We have found that the expression of HSP70, HSP90, and HSP27 is amplified and sustained during heat shock in NEAT1-depleted cells compared with control cells, indicating that NEAT1 feeds back via an unknown mechanism to regulate HSF1 activity. This interrelationship is potentially significant in human diseases such as cancer and neurodegenerative disorders.
Summary
Waste heat recovery helps reduce energy consumption, decreases carbon emissions, and enhances sustainable energy development. In China, energy‐intensive industries dominate the industrial ...sector and have significant potential for waste heat recovery. We propose a novel waste heat recovery system assisted by a heat pipe and thermoelectric generator (TEG) namely, heat pipe TEG (HPTEG)，to simultaneously recover waste heat and achieve electricity generation. Moreover, the HPTEG provides a good approach to bridging the mismatch between energy supply and demand. Based on the technical reserve on high‐temperature heat pipe manufacturing and TEG device integration, a laboratory‐scale HPTEG prototype was established to investigate the coupling performances of the heat pipes and TEGs. Static energy conversion and passive thermal transport were achieved with the assistance of skutterudite TEGs and potassium heat pipes. Based on the HPTEG prototype, the heat transfer and the thermoelectric conversion performances were investigated. Potassium heat pipes exhibited excellent heat transfer performance with 95% thermal efficiency. The isothermality of such a heat pipe was excellent, and the heat pipe temperature gradient was within 15°C. The TEG's thermoelectric conversion efficiency of 7.5% and HPTEG's prototype system thermoelectric conversion efficiency of 6.2% were achieved. When the TEG hot surface temperature reached 625°C, the maximum electrical output power of the TEG peaked at 183.2 W, and the open‐circuit voltage reached 42.2 V. The high performances of the HPTEG prototype demonstrated the potential of the HPTEG for use in engineering applications.
A novel waste heat recovery system is proposed assisted by a heat pipe and thermoelectric generator (TEG) namely, heat pipe TEG (HPTEG), to simultaneously recover waste heat and achieve electricity generation. Static energy conversion and passive thermal transport were achieved with the assistance of skutterudite TEGs and potassium heat pipes based on a laboratory‐scale HPTEG prototype. High TEGs thermoelectric conversion efficiency of 7.5% and TEG electrical output power of 183.2W were achieved.
High temperature seriously limits the annual production of fresh cut lilies, which is one of the four major cut flowers in the global cut flower market. There were few transcriptomes focused on the ...gene expression of lilies under heat stress. In order to reveal the potential heat response patterns in bulbous plants and provide important genes for further genetic engineering techniques to improve thermotolerance of lily, RNA sequencing of lilies under heat treatments were conducted.
In this study, seedlings of Lilium longiflorum 'White Heaven' were heat-treated at 37 °C for different lengths of time (0 h, 0.5 h, 1 h, 3 h, 6 h, and 12 h with a 12 h-light/12 h-dark cycle). The leaves of these lily seedlings were immediately collected after heat treatments and quickly put into liquid nitrogen for RNA sequencing. 109,364,486-171,487,430 clean reads and 55,044 unigenes including 21,608 differentially expressed genes (DEGs) (fold change ≥2) were obtained after heat treatment. The number of DEGs increased sharply during the heat treatments of 0.5 h-1 h and 1 h-3 h compared to that of other periods. Genes of the heat stress transcription factor (HSF) family and the small heat shock proteins (small HSPs, also known as HSP20) family responded to heat stress early and quickly. Compared to that of the calcium signal and hormone pathways, DEGs of the HSF-HSP pathway and reactive oxygen species (ROS) pathway were significantly and highly induced. Moreover, they had the similar expression pattern in response to heat stress. Small HSPs family genes were the major components in the 50 most highly induced genes at each heat stress treatment and involved in ROS pathway in the rapid response to heat stress. Furthermore, the barley stripe mosaic virus induced gene silencing (BSMV-VIGS) of LlHsfA2 caused a significantly reduced thermotolerance phenotype in Lilium longiflorum 'White Heaven', meanwhile decreasing the expression of small HSPs family genes and increasing the ROS scavenging enzyme ascorbate peroxidase (APX) genes, indicating the potential interplay between these two pathways.
Based on our transcriptomic analysis, we provide a new finding that small HSPs play important roles in crosstalk between HSF-HSP and ROS pathways in heat stress response of lily, which also supply the groundwork for understanding the mechanism of heat stress in bulbous plants.
•IR thermometry was utilized to measure temperature/and heat flux distributions.•Contributions of sensible/latent heat transfer were experimentally evaluated.•Phase change heat transfer is the ...dominant heat transfer mechanism in a PHP.
Experimental work was carried out to clarify the heat transfer mechanism of a pulsating heat pipe (PHP). A micro pulsating heat pipe (MPHP) with five turns was fabricated by engraving an interconnected micro-channel on a 1.1 mm thick transparent glass wafer. The engraved glass wafer and a 500 μm thick silicon wafer were anodically bonded to form a closed-loop MPHP. Ethanol was charged into the MPHP as the working fluid. The MPHP was vertically oriented with a bottom-heating mode. Using infrared (IR) thermometry, the distributions of temperature and heat flux were measured at the fluid-wall interface for the first time over the entire MPHP with high spatial and temporal resolution. High-speed flow visualization, which was synchronized to heat transfer measurements, was utilized to identify the local flow patterns corresponding to the local temperature and heat flux. The heat transfer at the fluid–silicon interface in the channels could be divided into the two parts: sensible heat transfer and latent heat transfer, and quantitative analysis of the data clarified the contributions of sensible/latent heat transfer to overall heat transfer. The overall contribution of latent heat transfer was estimated to be between 66% and 74%. Latent heat transfer not only induces the oscillating flow but also contributes significantly to overall heat transfer, whereas sensible heat transfer is a byproduct of the oscillating flow.
Various stress factors leading to protein damage induce the activation of an evolutionarily conserved cell protective mechanism, the heat shock response (HSR), to maintain protein homeostasis in ...virtually all eukaryotic cells. Heat shock factor 1 (HSF1) plays a central role in the HSR. HSF1 was initially known as a transcription factor that upregulates genes encoding heat shock proteins (HSPs), also called molecular chaperones, which assist in refolding or degrading injured intracellular proteins. However, recent accumulating evidence indicates multiple additional functions for HSF1 beyond the activation of HSPs. Here, we present a nearly comprehensive list of non-HSP-related target genes of HSF1 identified so far. Through controlling these targets, HSF1 acts in diverse stress-induced cellular processes and molecular mechanisms, including the endoplasmic reticulum unfolded protein response and ubiquitin–proteasome system, multidrug resistance, autophagy, apoptosis, immune response, cell growth arrest, differentiation underlying developmental diapause, chromatin remodelling, cancer development, and ageing. Hence, HSF1 emerges as a major orchestrator of cellular stress response pathways.
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