Thermal Buffering Capacity Research Articles

Design and properties of a new sustainable construction material based on date palm fibers and lime

Every year, huge quantities of date palm fibers (DPF) are produced and wasted all over the world. Using this natural fiber as raw material would contribute to the valorization of natural sustainable resources. This paper presents an experimental investigation of a new eco-material based on date palm fiber and lime. The experiments on the elaborated material investigate some mechanical, thermal, acoustic properties and moisture buffering capacity. The influence of the fiber/lime ratio on the behavior of the lightweight aggregate was studied systematically. The results of compressive strength testing indicated that PDF incorporation led to a reduction in resistance limit, however, the recorded average values are still acceptable. Also, it was observed that the thermal conductivity is sensitive to the variation of the fiber/lime composition ratio. The measured thermal conductivity reached a minimum of 0.091 W/m.K for samples of 50% fiber, which indicates that it can be used as a good thermal insulator. With regard to the sound absorption, the new material reveals good absorption capacity based on the measured sound absorption coefficient which is for 50% of fiber: for medium and high frequencies 0.65 and 0.55 respectively. Due to its porous morphology, the proposed material has the ability to absorb water vapor in a high relative humidity environment and to restore it in a dry one. Hence, it could therefore act as a hygric regulator. Measurements of moisture buffer value revealed that the material is classified as good or excellent depending on the percentage of fiber.

Riparian and geomorphic controls on thermal habitat dynamics of pools in a temperate headwater stream

AbstractStream pools serve as habitat for diverse communities composed of microbes, macroinvertebrates, and fish. Every pool presents a combination of geomorphological features, and each pool habitat hosts a unique community. These communities are tied to the physical characteristics of their habitat, especially water temperature. The effects of geomorphology and hydraulic variables on thermal habitat dynamics in pools are not well understood. In this study, the thermal regime in important stream pool habitats was investigated in relation to their riparian and geomorphological features. Our results indicate that instream wood, groundwater resurgence, and depth can locally modify the pool thermal habitat and increase thermal buffering capacity during heat‐stress events. Our findings highlight the importance of riparian vegetation and in‐channel hydrogeomorphic features in controlling pool thermal habitats.

Thermal buffering performance of composite phase change materials applied in low-temperature protective garments

Phase change material (PCM) is increasingly being applied in the manufacturing of functional thermo-regulated textiles and garments. This paper investigated the thermal buffering performance of different composite PCMs which are suitable for the application in functional low-temperature protective garments. First, according to the criteria selecting PCM for functional textiles/garments, three kinds of pure PCM were selected as samples, which were [Formula: see text]-hexadecane, [Formula: see text]-octadecane and [Formula: see text]-eicosane. To get the adjustable phase change temperature range and higher phase change enthalpy, three kinds of composite PCM were prepared using the above pure PCM. To evaluate the thermal buffering performance of different composite PCM samples, the simulated low-temperature experiments were performed in the climate chamber, and the skin temperature variation curves in three different low temperature conditions were obtained. Finally composite PCM samples’ thermal buffering time, thermal buffering capacity and thermal buffering efficiency were calculated. Results show that the comprehensive thermal buffering performance of [Formula: see text]-octadecane and [Formula: see text]-eicosane composite PCM is the best.

Thermally buffered corrugated packaging for preserving the postharvest freshness of mushrooms (Agaricus bispours)

This research successfully developed a novel thermally buffered package using a paraffin-based thermo regulating material (5 °C) microencapsulated in melamine powder (MMP). MMP was used to coat a poly-textile, and the results were compared with those of a commercially available TRM (temperature regulating material), i.e., tetradecane. The major real-world difficulty of containing the liquid phase was overcome in this study via microencapsulation. A corrugated package constructed of MMP poly-textile and lined with LDPE bag liners containing 400 g of MMP provided a sufficient thermal buffering capacity to maintain the temperature inside the package at 5 °C while the package was held at ambient temperature for 30–60 min. A similar experiment with mushrooms (Agaricus bispours) packed inside the thermally buffered package was performed to determine whether it could provide effective thermal buffering during transport and temporary storage. The MMP and MMP-coated poly-textile were characterized using TGA, DSC, SEM, and FTIR to evaluate their thermal, chemical, and morphological properties. The quality of the mushrooms packed into the thermally buffered package was determined by measuring the pH, color, texture, weight loss, and PPO activity. The thermally buffered package, which combines the effects of a pure MMP bag liner and an MMP + poly-textile package, demonstrated excellent ability to control temperature. All of the quality aspects of the mushrooms were within acceptable limits during the storage study. This developed package will solve some of the restrictions faced by mushroom producers and distributers in order to maintain stable quality throughout the storage period.

Thermal buffering capacity of the germination phenotype across the environmental envelope of the Cactaceae.

Recruitment from seeds is among the most vulnerable stage for plants as global temperatures change. While germination is the means by which the vast majority of the world's flora regenerate naturally, a framework for accurately predicting which species are at greatest risk of germination failure during environmental perturbation is lacking. Taking a physiological approach, we assess how one family, the Cactaceae, may respond to global temperature change based on the thermal buffering capacity of the germination phenotype. We selected 55 cactus species from the Americas, all geo-referenced seed collections, reflecting the broad environmental envelope of the family across 70° of latitude and 3700m of altitude. We then generated empirical data of the thermal germination response from which we estimated the minimum (Tb ), optimum (To ) and ceiling (Tc ) temperature for germination and the thermal time (θ50 ) for each species based on the linearity of germination rate with temperature. Species with the highest Tb and lowest Tc germinated fastest, and the interspecific sensitivity of the germination rate to temperature, as assessed through θ50 , varied tenfold. A left-skewed asymmetry in the germination rate with temperature was relatively common but the unimodal pattern typical of crop species failed for nearly half of the species due to insensitivity to temperature change at To . For 32 fully characterized species, seed thermal parameters correlated strongly with the mean temperature of the wettest quarter of the seed collection sites. By projecting the mean temperature of the wettest quarter under two climate change scenarios, we predict under the least conservative scenario (+3.7°C) that 25% of cactus species will have reduced germination performance, whilst the remainder will have an efficiency gain, by the end of the 21st century.

Quantifying deforestation and forest degradation with thermal response

Deforestation and forest degradation cause the deterioration of resources and ecosystem services. However, there are still no operational indicators to measure forest status, especially for forest degradation. In the present study, we analysed the thermal response number (TRN, calculated by daily total net radiation divided by daily temperature range) of 163 sites including mature forest, disturbed forest, planted forest, shrubland, grassland, savanna vegetation and cropland. TRN generally increased with latitude, however the regression of TRN against latitude differed among vegetation types. Mature forests are superior as thermal buffers, and had significantly higher TRN than disturbed and planted forests. There was a clear boundary between TRN of forest and non-forest vegetation (i.e. grassland and savanna) with the exception of shrubland, whose TRN overlapped with that of forest vegetation. We propose to use the TRN of local mature forest as the optimal TRN (TRNopt). A forest with lower than 75% of TRNopt was identified as subjected to significant disturbance, and forests with 66% of TRNopt was the threshold for deforestation within the absolute latitude from 30° to 55°. Our results emphasized the irreplaceable thermal buffer capacity of mature forest. TRN can be used for early warning of deforestation and degradation risk. It is therefore a valuable tool in the effort to protect forests and prevent deforestation.

Strength and Stiffness of Stabilized Alluvial Silt under Frost Actions

The Yellow River alluvial silt was stabilized into pavement base materials for cold regions. The stabilizing additives were cement, fly ash, and lime, which were included in a range of combinations and dosages when mixed with the silt. Freeze-thaw cyclic impacts were conducted on the treated samples to assess materials performance of withstanding the frost actions. The tests were conducted on samples cured for 7 days to up to 180 days. Test results show that the cement-fly ash-treated samples outperform the other two stabilization categories with respect to material strength and stiffness developed under both normal and frost conditions. Under the normal conditions, the material unconfined compressive (UC) strength rises to 3.0 MPa on day 28 depending on the cement and fly ash dosage used. If subjected to frost actions, the fly ash inclusions warrant a residual UC strength value of 1.3 MPa and above. The antifrost performance of the cement-fly ash-treated samples is related to thermal buffer capacity of the fly ash particles. Water adsorption and material soundness results agree with the strength and stiffness development. An optimal dosage was 3–6% for the cement and 0.3 for cement to fly ash mass ratio.

Development of an encapsulated phase change material via emulsion and coaxial electrospinning

ABSTRACTThis article reports on the encapsulation of a phase change material (PCM) into a hydrophilic polymer, poly(vinyl alcohol) (PVOH), by means of electrospinning. Different strategies were carried out to improve the thermal buffering capacity and the stability of the developed structures when they were exposed to different relative humidity (RH) conditions. On the one hand, the thermal energy storage capacity of PVOH/PCM structures obtained through emulsion electrospinning was optimized by using different amounts of polyoxyethylene sorbitan monolaureate (Tween 20). Surfactant addition successfully increased the heat storage capacity of the developed structures, reaching an optimum performance at a concentration of 0.32% in weight with respect to the total emulsion weight. However, the hydrophilic nature of the developed structures made them extremely difficult to handle due to swelling with increasing RH. To avoid this issue an additional shell layer of poly(caprolactone) (PCL), was applied by coaxial electrospinning. In this case, the PVOH/PCM ratio (core) was optimized to reach the highest heat storage capacity per gram of sample and, then, a PCL solution was used as a shell material to hydrophobize the structures. The optimized coaxial electrospun structures were able to encapsulate about 82% of PCM. The use of both emulsion and coaxial electrospinning strategies are introduced here for the first time as advanced strategies to overcome application issues such as unintended migration and performance drop in the previously developed monophase materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43903.

Cold Tolerance of Halyomorpha halys (Hemiptera: Pentatomidae) Across Geographic and Temporal Scales.

The brown marmorated stink bug, Halyomorpha halys (Stål), is native to eastern Asia and is presently invading North America. Little is known about the exposure to and effects of winter temperatures in newly invaded regions on H. halys The overwintering habitats that this species utilizes vary greatly in their thermal buffering capacity. They naturally overwinter in aggregations beneath loose bark on trees and in cliff outcroppings, but will also commonly aggregate in buildings. Effects of cold temperatures such as mortality and freezing have yet to be quantified in the invading population. We report that H. halys is chill intolerant (i.e., dies before reaching its freezing point), and that the degree of cold tolerance of populations in North America differs by season, sex, and acclimation location. The mean winter supercooling point (± SEM) of individuals acclimated in Minnesota was -17.06 °C ± 0.13 and in Virginia was -13.90 °C ± 0.09. By using laboratory assays of lower lethal temperatures and ambient air temperature records, we accurately forecasted mortality for field experiments in Minnesota and Virginia. Temperature refugia provided by human-built structures are likely crucial for overwintering survival during atypically cold winters and possibly contribute to the northern geographic range expansion of this economically damaging insect in the temperate climates of North America.

Thermal buffering effect of alpine boulder field microhabitats in Australia: Implications for habitat management and conservation

Identifying and protecting microhabitats with conservation value is becoming a high priority for conservationists under projected climate change. Information on the buffering effects of microhabitats and its major drivers is a prerequisite to implementing effective conservation. We collected hourly temperature data from 70 alpine–subalpine sites nested within 9 boulder field clusters in an area measuring approximately 60km×30km in New South Wales, Australia, over a period of more than 2years. We studied the thermal buffering effect of the boulder fields and investigated the factors driving the effect using multilevel (i.e., sampling points nested within boulder field clusters) regression modeling. We found remarkable seasonal and spatial variations in the thermal buffering effect of boulder fields. Boulder fields buffered the surface temperature maxima by 2.91°C at a depth of 50cm and 4.39°C at a depth of 100cm, while they buffered the surface temperature minima by 0.54°C at the depth of 50cm and 1.36°C at the depth of 100cm, with temperature range reduced by 3.45°C and 6.48°C in warmer period and by 1.23°C and 2.05°C in colder period at two depths. We defined thermal buffering in temperature ranges as the thermal buffering capacity (TBC) as an exemplar for multilevel modeling. We found that vegetation cover and elevation affected the TBC at the point level, whereas the aspect and inclination of slopes affected the TBC at the cluster level. These findings are instructive for the protection of habitats, as high priority should be given to those habitats that offer effective TBC. Furthermore, the environmental factors identified to be driving TBC provide important input to the management of species habitats.

Recycling Wood Composite Panels: Characterizing Recycled Materials

Downgraded medium density fiberboard (MDF), particleboard (PB), and oriented strandboard (OSB) panels were individually subjected to steam explosion treatment. Downgraded MDF and PB panels were separately treated with thermal chemical impregnation using 0.5% butanetetracarboxylic acid (BTCA). And downgraded PB panels were processed with mechanical hammermilling. The pH, buffer capacity, fiber length, and particle size of these recycled materials were evaluated. After the steam explosion and thermal chemical impregnation treatments, the pH and buffer capacity of recycled urea formaldehyde resin (UF)-bonded MDF and PB furnishes increased and the fiber length decreased. The hammermilling of recycled PB was less likely to break particles down into sizes less than 1 mm2.

Heat transfer study of submicro-encapsulated PCM plate for food packaging application

In recent studies, encapsulated phase change materials (PCM) were developed as novel materials for food packaging because of their improved thermal insulation capacity. The PCMs (often liquid in room temperature) are encapsulated in a shell material so as they can be practically handled. In this work, the thermal behaviour of an encapsulated PCM material (Rubitherm RT5 encapsulated in polycaprolactone PCL) with two different PCM mass fractions was studied. The model was validated by experimental cooling and heating processes, under controlled air temperature conditions. The numerical result demonstrated a better thermal buffering capacity of the encapsulated PCM material compared to a standard one (cardboard).

The importance of underground shelter resources for reptiles in dryland landscapes: A woma python case study

AbstractFor effective fauna conservation and management, ecologists are required to identify the resources that are critical for species to survive, and consider how these are distributed across landscapes. The critical resources usually considered are food and water, but the availability of appropriate shelter resources can be a key driver of habitat suitability for terrestrial reptiles and amphibians. Reptiles are important components of dryland ecosystems, yet we have little understanding about how anthropogenic disturbances affect the availability of shelter resources and reptile survival in drylands. In this study, we used VHF radio‐tracking to assess the importance of shelter resources in determining the habitat use patterns of a Near‐Threatened reptile species, the woma (Aspidites ramsayi; Pythonidae), in modified and intact dryland landscapes of Queensland, Australia. We compared the structural and thermal attributes of locations that were used, with those that were available. Using an information‐theoretic approach, we found that the occurrence of womas was strongly associated with the presence of ground burrows, which are excellent thermal insulators. No other shelter type was capable of buffering our study species from sub‐zero temperatures during winter, although summer temperatures of >40°C were buffered by hollow logs and piles of woody debris. Habitat use patterns were influenced more by the occurrence of underground shelters than by habitat type. Clearing status per se (cleared, regrowth or intact) had minimal influence on occurrence. Thermally buffered underground shelters are a vital resource for our focal species, and the availability of this shelter resource drives habitat suitability in modified dryland landscapes. Due to the key trophic role of reptiles in dryland ecosystems, and the excellent thermal buffering capacity of underground shelters, we propose that ground burrows may be potentially considered as keystone structures in drylands, and require a similar level of protection to ‘habitat’ or ‘legacy’ trees in forested ecosystems.

Modelling and validation of robust partial thawing of frozen convenience foods during distribution in the cold chain

In collaboration with two commercial distributors we have tested a new concept for distribution, where convenience products for the food service industry are prepared, frozen and packed in cardboard boxes, but distributed in the chill chain at +5°C instead of in the frost chain. This will lead to a partial thawing before reaching the end user. The high thermal buffering capacity of the product under thawing ensures that the product temperature remains stable at subzero temperatures, also in cases of temperature abuse for some hours. To investigate and validate the concept, cardboard boxes packed with small blocks of a frozen model food (23 pct. Tylose® gel) and quipped with temperature loggers were distributed by trucks operating in the cold chain. In addition, controlled storage and temperature abuse experiments were conducted. To predict the product temperature–time relationship we developed a new thawing model for the slow thawing of food pieces packed in a box. The model is based on enthalpy balances under quasi-stationary conditions; a condition that is fulfilled in the practical distribution experiments. The experiments confirmed the model predictions that the products were still partially frozen even after two days or more of distribution at +5oC, and that the temperatures inside the product and in the middle of the box were quite stable against the normal oscillations of the ambient temperature in the cold chain. The product temperature was also robust against temperature abuse, as predicted. The new distribution method not only has the potential of prolonging product shelf life but also gives the distributors an increased flexibility in the distribution chain.

Composite nano-structured calcium silicate phase change materials for thermal buffering in food packaging

A new nano-structured calcium silicate (NCS) – phase change composite material has been developed to provide effective thermal buffering for paperboard packages during the transport and temporary storage of chilled perishable food from the supplier to the market. NCS is a proprietary material comprising nano-size platelets stacked together in a unique open framework structure having a high pore volume and liquid absorbency. Alkane phase change materials (PCMs) which absorb and release latent heat energy (∼160–190Jg−1) can be used in heat storage and release applications as they are non-toxic and their operating temperature range can be tuned by the hydrocarbon chain length. The major practical problem of containing the liquid phase has been overcome here by incorporating the alkane PCM (Rubitherm RT6, melting point 8°C) into the highly porous NCS matrix to a level of about 300 wt% of NCS. A paperboard container constructed and lined with six bubble wrap “Post-It” bags containing 400g NCS-300PCM composite provided sufficient thermal buffering capacity to maintain the temperature inside the container at 10°C for some 5h after the outside temperature had increased to about 23°C. A similar performance was obtained when the container was filled with 2kg of asparagus, as a model for perishable food. The NCS-300PCM composite therefore provides sufficient thermal buffering to ensure perishable food in a paperboard container remains below 10°C during transport and temporary storage en route from the supplier to the market.

Ecosystem Thermal Buffer Capacity as an Indicator of the Restoration Status of Protected Areas in the Northern Ethiopian Highlands

Abstract Restoration status of forest rehabilitation areas can be assessed by comparing their ecosystem characteristics with those of a reference system, most often what is considered the natural climax vegetation. However, comprehensive measurements needed for a traditional vegetation description are often hard or impractical in complex (sub)tropical ecosystems. Therefore, an alternative approach is the identification of simple indicators of ecosystem integrity. The use of such indicators can speed up the availability of resource inventories and thus contribute to the accelerated implementation of successful rehabilitation practices. Thermal buffer capacity (TBC) of ecosystems has been previously proposed as an overall indicator of ecosystem integrity. In this article, sequential surface‐temperature measurements are proposed as a method for TBC assessment of different land‐use types. Surface temperatures of seven land units in central Tigray (northern Ethiopia), each with a uniform land‐use type (degraded and bushy grazing land, enriched and non‐enriched rehabilitation area, and forest), were measured with a hand‐held infrared thermometer in the rainy and the dry season. Surface‐temperature models were derived by means of quadratic regression. Cross‐correlation functions were calculated for all possible pairs of land‐unit time‐series data. Instantaneous heat‐up rates, average TBC, and accumulated heat load were calculated. Repeated‐measures analysis of variance was used to test the effect of aspect and protection status on TBC. Kruskal–Wallis one‐way analysis of variance by ranks for small samples was used to test the significance of differences in heat‐up rates and heat load among land‐use groups. Time lags between land‐unit surface temperatures are caused by differences in aspect rather than land‐use type. Protection status and aspect have a significant effect on the average TBC. Results clearly demonstrate a differentiation between protected (low heat‐up rate) and non‐protected areas (high heat‐up rate). Overall ranking suggests that the remnant forest has the highest TBC of all surveyed land‐use types, followed by the enriched protected area. Results of this study show that TBC quickly responds to area closure and can therefore be used to monitor the development of protected areas. It is strongly recommended that a detailed monitoring strategy for protected areas on the basis of this technology be devised, validated, and finally transferred to the local communities.

ATMOSPHERIC CHANGE AND BIODIVERSITY

Strategies to conserve biodiversity need to include the monitoring, modelling, adaptation and regulation of the composition of the atmosphere. Atmospheric issues include climate variability and extremes; climate change; stratospheric ozone depletion; acid deposition; photochemical pollution; suspended particulate matter; and hazardous air pollutants. Coarse filter and fine filter approaches have been used to understand the complexity of the interactions between the atmosphere and biodiversity. In the first approach, climate-based models, using GIS technology, helped create future biodiversity scenarios under a 2 × CO2 atmosphere. In the second approach, the SI/MAB forest biodiversity monitoring protocols helped calibrate the climate-forest biodiversity baseline and, as global diagnostics, helped identify where the biodiversity was in equilibrium with the present climate. Forest climate monitoring, an enhancing protocol, was used in a co-location approach to define the thermal buffering capacity of forest ecosystems and their ability to reduce and ameliorate global climate variability, extremes and change.