Thermal Preconditioning Research Articles

Thermal preconditioning of membrane stress to control the shapes of ultrathin crystals.

We employ the phospholipid bilayer membranes of giant unilamellar vesicles as a free-standing environment for the growth of membrane-integrated ultrathin phospholipid crystals possessing a variety of shapes with 6-fold symmetry. Crystal growth within vesicle membranes, where more elaborate shapes grow on larger vesicles is dominated by the bending energy of the membrane itself, creating a means to manipulate crystal morphology. Here we demonstrate how cooling rate preconditions the membrane tension before nucleation, in turn regulating nucleation and growth, and directing the morphology of crystals by the time they are large enough to be visualized. The crystals retain their shapes during further growth through the two phase region. Experiments demonstrate this behavior for single crystals growing within the membrane of each vesicle, ultimately comprising up to 13% of the vesicle area and length scales of up to 50 microns. A model for stress evolution, employing only physical property data, reveals how the competition between thermal membrane contraction and water diffusion from tensed vesicles produces a size- and time-dependence of the membrane tension as a result of cooling history. The tension, critical in the contribution of bending energy in the fluid membrane regions, in turn selects for crystal shape for vesicles of a given size. The model reveals unanticipated behaviors including a low steady state tension on small vesicles that allows compact domains to develop, rapid tension development on large vesicles producing flower-shaped domains, and a stress relaxation through water diffusion across the membrane with a time constant scaling as the square of the vesicle radius, consistent with measurable tensions only in the largest vesicles.

Influence of severe thermal preconditioning on the bond between carbon FRCM and masonry substrate: Effect of textile pre-impregnation

Fabric-reinforced cementitious matrix (FRCM) composites often include polymer-impregnated bundles to improve the exploitation of the textile mechanical properties. However, organic components may degrade when exposed to elevated temperature. In this paper, the bond behavior of a carbon FRCM applied to a masonry substrate and exposed to a thermal preconditioning up to 300 °C for 250 min is investigated. Tensile tests on the textile and flexural and compression tests on the mortar matrix, as well as single-lap direct shear tests of FRCM-masonry joints with bare and impregnated textiles, are performed. Results show that the polymeric impregnation improves the mechanical properties of the FRCM even after thermal preconditioning.

Thermal Preconditioning Alters the Stability of Hump-Snout Whitefish (Coregonus fluviatilis) and Its Hybrid Form, Showing Potential for Aquaculture.

One of the little-studied ways that climate warming or temperature increases in aquaculture could affect aquatic animals is through accelerated aging. This study is dedicated to understanding the principles of molecular and cellular aging in the target tissues of juvenile whitefishes (Yenisei hump-snout whitefish and its hybrid) under the influence of acute heat stress (up to 26 °C), and the effects of thermal preconditioning as pre-adaptation. Non-adapted stressed hump-snout whitefish showed a higher induction threshold for functionally active mitochondria in the blood and a decrease in telomerase activity in the liver after heat shock exposure as a long-term compensatory response to prevent telomere shortening. However, we observed heat-induced telomere shortening in non-adapted hybrids, which can be explained by a decrease in mitochondrial membrane stability and a gradual increase in energy demand, leading to a decrease in protective telomerase activity. The pre-adapted groups of hump-snout whitefish and hybrids showed a long-term or delayed response of telomerase activity to heat shock, which served as a therapeutic mechanism against telomere shortening. We concluded that the telomerase and telomere responses to thermal stress demonstrate plasticity of tolerance limits and greater stability in hump-snout whitefish compared with hybrids.

Thermal preconditioning can reduce the incidence of intraoperatively acquired pressure injuries

Intraoperatively acquired pressure injuries (IAPIs) occur frequently among patients who undergo surgical procedures that last longer than 3 h. Several studies indicated that heat shock proteins (HSPs) play an important role in the protection of stress-induced damages in skin tissues. Hence, the aim of this study was to investigate the potential preventive effect of thermal preconditioning (TPC) on IAPIs in surgical patients and rats and to identify the differentially expressed HSP genes in response to the above treatment. TPC was performed on one group of hairless rats before the model of pressure injuries was established. Subsequently, the size of skin lesions was measured and the expression levels of mRNA and protein of HSPs of the pressured skin were detected by real-time polymerase chain reaction (RT-PCR), western blot, and immunohistochemical staining. For human studies, 118 surgical patients were randomly divided into the TPC group (n = 59) and the control group (n = 59), respectively. The temperature and pressure of sacral skin, as well as the incidence of pressure injury (PI) were detected and compared. In animal studies, TPC significantly reduced both the size and incidence of PI in rats on the second, third and fourth days post treatment. In addition, the expression levels of both mRNA and protein of HSP27 were increased in the TPC group, compared with the control group. Immunohistochemical staining showed that HSP27 was distributed in various types of dermal cells and increased in basal cells. In human studies, a significant reduction (75%) of IAPIs was observed among the patients in the TPC group. TPC can reduce the incidence of PI in rats and humans, and the upregulation of HSP27 may play an important role in this biological progress. Further studies are warranted to explore the molecular mechanism of the preventive effect in PI mediated by HSP27.

The Effect of Preconditioning Temperature on Gas Permeability of Alkali-Activated Concretes.

Alkali-activated materials (AAM) are binders that are considered an eco-friendly alternative to conventional binders based on Portland cement. The utilization of industrial wastes such as fly ash (FA) and ground granulated blast furnace slag (GGBFS) instead of cement enables a reduction of the CO2 emissions caused by clinker production. Although researchers are highly interested in the use of alkali-activated concrete (AAC) in construction, its application remains very restricted. As many standards for hydraulic concrete's gas permeability evaluation require a specific drying temperature, we would like to emphasize the sensitivity of AAM to such preconditioning. Therefore, this paper presents the impact of different drying temperatures on gas permeability and pore structure for AAC5, AAC20, and AAC35, which contain alkali-activated (AA) binders made from blends of FA and GGBFS in slag proportions of 5%, 20%, and 35% by the mass of FA, respectively. The preconditioning of samples was performed at 20, 40, 80, and 105 °C, up to the obtainment of constant mass, and then gas permeability was evaluated, as well as porosity and pore size distribution (mercury intrusion porosity (MIP) for 20 and 105 °C). The experimental results demonstrate up to a three-percentage-point rise in the total porosity of low-slag concrete after 105 °C in comparison to 20 °C, as well as a significant increase in gas permeability, reaching up to 30-fold amplification, contingent upon the matrix composition. Notably, the alteration in pore size distribution, influenced by the preconditioning temperature, exhibits a substantial impact. The results highlight an important sensitivity of permeability to thermal preconditioning.

(1270) Thermal Preconditioning During EVLP Reduces T Lymphocytes and Increases Monocytes and Neutrophils Contents in the Perfusion Solution

(1270) Thermal Preconditioning During EVLP Reduces T Lymphocytes and Increases Monocytes and Neutrophils Contents in the Perfusion Solution

Effects of juvenile thermal preconditioning on the heat-shock, immune, and stress responses of rainbow trout upon a secondary thermal challenge

Higher water temperatures and pathogens are both significant factors that negatively affect the welfare of teleost fish. In aquaculture, compared to natural populations, these problems are especially exacerbated, as the animals have relatively limited mobility, and the higher density promotes faster spread of infectious diseases. Because of the potential harm these stressors can inflict, methods that can limit the damage of these stressors are particularly valuable. As a method of interest, early-life thermal preconditioning of animals demonstrated some potential for effective improvements in thermotolerance. However, the potential effects of the method on the immune system via the heat-stress model have not been explored. In this experiment, juvenile-stage thermal preconditioned rainbow trout (Oncorhynchus mykiss) were subjected to a secondary thermal challenge, animals were collected and sampled at the time of lost equilibrium. The effects of preconditioning on the general stress response was assessed by measuring the plasma cortisol levels. In addition, we also examined hsp70 and hsc70 mRNA levels in the spleen and gill tissues, as well as IL-1β, IL-6, TNF-α, IFN-1, β2m, and MH class I transcripts via qRT-PCR. No changes in CTmax were observed between the preconditioned and control cohorts upon the second challenge. IL-1β and IL-6 transcripts were generally upregulated with increased temperature of the secondary thermal challenge, whereas IFN-1 transcripts were upregulated in the spleen, but downregulated in the gills, along with MH class I. The juvenile thermal preconditioning produced a series of changes in transcript levels for IL-1β, TNF-α, IFN-1, and hsp70 but the dynamics of these differences were inconsistent. Finally, analysis of plasma cortisol levels presented significantly lower cortisol levels in the pre-conditioned animals compared to the non-pre-conditioned control cohort.

(Invited) Opportunities for Bulk Silicon As a High Capacity Lithium Host

Silicon, the earth’s second most abundant element ushered in new age of computing capability. More recently, silicon is enjoying a second wave of technological adoption as a constituent of lithium-ion battery negative electrodes; made possible in practice by reducing the dimensions to the nanoscale and/or compositing with traditional carbon-based lithium host materials. The large lithium capacity and subsequent volumetric expansion and mechanical fracture have been documented extensively and the nano and composite routes mentioned above provide strategies to overcome this obstacle. We take a new exploratory approach elevating the working temperature to demonstrate reversible alloying and dealloying of lithium and silicon, in its most basic bulk form, a wafer. The brittle nature of silicon may be made more elastic when operated above its brittle-to-ductile transition temperature, potentially leading to more elastic behavior capable of maintaining its structure with modulation of its volume. Here was explore lithium alloying/dealloying into bulk silicon at elevated temperature to assess the efficiently and reversibility of silicon in this environment. While a contrived experiment, we are learning more about lithium diffusion into silicon and may provide a thermal preconditioning of silicon electrode materials to support long cycle for lithium-ion batteries. Additionally, the developmental improvements of a high temperature electrochemical cell will be conveyed along with demonstration of an electrolyte salt, LiTFI, in the molten form. Last, micro computed tomography 3D images will be presented to show crack formation and progression when alloying a bulk silicon wafer with lithium at elevated temperatures.

Lung Function and Inflammatory Profiling of Damaged Rat Donor Lungs Following EVLP Thermal Preconditioning

<h3>Purpose</h3> Ex-vivo lung perfusion (EVLP) is a validated technique allowing evaluation and reconditioning of damaged donor lungs to make them suitable for transplantation. Moderate hyperthermia is known to exert cytoprotective effect, via induction and accumulation of specific proteins, known as heat shock proteins (HSPs). We hypothesized that thermal preconditioning (TP) with a well-calibrated heat stress applied during EVLP could improve lung graft by reduction of oxidative stress, cell death and inflammation. <h3>Methods</h3> Male rats were randomly assigned into 2 groups: controls (Ctrl, n=5) or TP (n=5). In both groups, lungs were kept <i>in situ</i> for 1h at room temperature, then flushed with cold Perfadex. Heart-lung block was harvested and kept at 4°C for 1h, then mounted on the EVLP system for 3h. In Ctrl group, the temperature perfusion solution was kept at 37°C the all-time. In the TP group, a heat shock was done for 30 minutes after 1h of EVLP by heating the perfusion solution at 41.5°C. At the end of EVLP, lungs were snap-frozen and kept at -80°C for further tissue analysis. <h3>Results</h3> Static pulmonary compliance, peak inspiratory pressure, and oxygenation capacity were similar in both groups. We were able to induce HSPs in the TP group (<i>Hspa1a</i> and <i>Hmox-1</i>). In the TP group, we observed a reduction of oxidative stress (carbonyls and MDA), a decrease of apoptosis (Caspase 3 and 7) and a decrease of pro-inflammatory NF-κB transcription factor as well as the expression of inflammation mediators such as TNF-α, IL-1α, IL-1β, CXCL-1 and CCL-2. <h3>Conclusion</h3> Thermal preconditioning during EVLP decreased oxidative stress, apoptotic cell death, and inflammation of damaged lungs. These findings demonstrate that EVLP in association with thermal preconditioning could be a promising therapeutic platform improving lung quality of damaged donor lungs.

Transient Heat Stress During Ex-Vivo Lung Perfusion Induces the Heat Shock Response and Preserves Lung Function in Pig Model

<h3>Purpose</h3> The heat shock response (HSR) is a highly conserved adaptative response to thermic stress, related to the induced expression of heat shock proteins (HSPs) which promote significant cytoprotection. We hypothesized that thermal preconditioning (TP) with a well-calibrated heat stress (HS) applied during EVLP elicits a HSR and improves lung graft function by interfering with immune inflammation and oxidative stress pathways. <h3>Methods</h3> Donor lungs (n=12) underwent extended hypothermic preservation of 16h. Lungs were assigned into two groups: 1) Control (n=6): 4h EVLP at 37°C; and 2) TP, (n=6): normothermic EVLP (37°C, 2h), followed by hyperthermic EVLP (42°, 30min), and normothermic EVLP (37°C, 1.5h). Ex-vivo lung function was assessed by measuring airway pressure, lung compliance and pulmonary vascular resistance. We determined expression of HSPs in tissue, and lung damage and oxidative stress biomarkers in tissue, BAL and perfusate at multiple time points. <h3>Results</h3> Lungs undergoing thermal preconditioning (TP group) showed significantly lower pulmonary arterial pressure and vascular resistance, increased dynamic and static pulmonary compliance and reduced airway pressure with no changes in oxygenation capacity as compared to lungs in the control group. At the end of EVLP, lungs in TP group had significant increase of lung mRNA of Hspa1a, Hsc70 and Hmox-1, reduction of nitrotyrosine (3-NT) in lung tissue, and reduction of LDH, CK18-M30 and proteins in BAL fluid. TP during ELVP decreased the expression of TNFα, IL6/IL10, MPO and IL-8 in BAL consistent with inflammasome inhibition. <h3>Conclusion</h3> Transient heat stress during EVLP induces HSR and reduces nitroxidative stress, cellular injury and edema, and prevents functional deterioration of pig lungs after extended cold ischemia. These data indicate the therapeutic potential of thermal preconditioning as a way to recondition damaged lungs and to improve current preservation strategies.

Lung Function and Inflammatory Profiling of Damaged Rat Donor Lungs Following EVLP Heat Stress with Different Temperatures

<h3>Purpose</h3> Ex-vivo lung perfusion (EVLP) is a validated technique allowing evaluation and reconditioning of damaged donor lungs to make them suitable for lung transplantation. Moderate hyperthermia is known to exert cytoprotective effect, via induction and accumulation of specific proteins, known as heat shock proteins (HSPs). We hypothesized that thermal preconditioning (TP) with a well-calibrated heat stress applied during EVLP could improve lung graft by reduction of oxidative stress, cell death and inflammation. <h3>Methods</h3> Male rats were randomly assigned into 5 groups: controls (Ctrl, n=5) and four heat stress groups (HS of 41.5°C; 42.0°C; 42.5°C or 43.5°C, n=5). In all groups, lungs were kept <i>in situ</i> for 1h at room temperature, then flushed with cold Perfadex. Heart-lung block was harvested and kept at 4°C for 1h, then mounted on the EVLP system for 3h. In Ctrl group, the temperature perfusion solution was kept at 37°C the all-time. In the HS groups, a heat shock was done for 30 minutes after 1h of EVLP by heating the perfusion solution at different temperature. At the end of EVLP, lungs were snap-frozen and kept at -80°C for further tissue analysis. <h3>Results</h3> Static pulmonary compliance SPC ratio (180 min to 60 min of EVLP) was significantly increased in the 41.5°C group compared to Ctrl group, while it was significantly reduced in 43.5°C group. The weight gain was significantly reduced in 41.5°C, whereas increased in 43.5°C group. In all HS groups, except in 43.5°C, protein levels of inducible HSP72 and Heme oxygenase-1 (HO-1) were significantly increased compared to Ctrl. Reduction of caspase 3 activation (apoptosis marker) was seen in all groups but reached significant level only in 41.5°C and 43.5°C groups. In all HS groups, we could see a reduction of inflammatory mediators such as, IL-1α, IL-1β, and TNF-α, a reduction of the release of CC16 (a marker of lung epithelial injury), as well as a reduction of IL-1β in Steen solution. <h3>Conclusion</h3> Thermal preconditioning during EVLP can decrease apoptotic cell death and inflammation of damaged lungs. These findings demonstrate that EVLP in association with well calibrated thermal preconditioning (41.5°C) could be a promising therapeutic platform improving lung quality of damaged donor lungs.

Experimental Studies of the Heat Exchange Between the Water Film and the Casting Roller in the Thermal Preconditioning Chamber

When the casting roller is cooled or heated in the preconditioning chamber the water is supplied to its surface by flat-jet nozzles. The visual inspection of the model of the casting roller showed that a considerable part of it can be covered with the water film spreading from sprinkling zones. It was established that the heat conductivity in the roller body is considered to be a crucial thermal preparation factor in the conjugate heat-exchange problem for the roller of a large diameter at Bio criterion values exceeding 20. Hence, it is sufficient to provide an essential level of the heat transfer that corresponds to the heat transfer coefficient of 2000 W/(m2∙K) to provide appropriate operating conditions for the thermal preparation of the roller. The conditions are also met in sprinkling zones. Due to this fact this scientific paper studies the heat exchange conditions under the water film that spreads between the adjacent sprinkling zones. A range of changes in the flow rate of the spreading water film was determined experimentally. The conditions of heat exchange between the surface of alpha-calorimeter and the water film were analyzed depending on its flow rate and the heat meter surface temperature. A generalized correlation equation was derived. It was established that the heat exchange intensity in sprinkling zones and under the spreading water film meets technological roller treatment conditions in the preconditioning chambers. The obtained research data can be used for the rational arrangement of the collectors and flat-jet nozzles in casting roller preconditioning chambers to reduce the cold and hot water consumption and cut down operating costs.

Identification of a novel compound that simultaneously impairs the ubiquitin-proteasome system and autophagy

ABSTRACT The ubiquitin-proteasome system (UPS) and macroautophagy/autophagy are the main proteolytic systems in eukaryotic cells for preserving protein homeostasis, i.e., proteostasis. By facilitating the timely destruction of aberrant proteins, these complementary pathways keep the intracellular environment free of inherently toxic protein aggregates. Chemical interference with the UPS or autophagy has emerged as a viable strategy for therapeutically targeting malignant cells which, owing to their hyperactive state, heavily rely on the sanitizing activity of these proteolytic systems. Here, we report on the discovery of CBK79, a novel compound that impairs both protein degradation by the UPS and autophagy. While CBK79 was identified in a high-content screen for drug-like molecules that inhibit the UPS, subsequent analysis revealed that this compound also compromises autophagic degradation of long-lived proteins. We show that CBK79 induces non-canonical lipidation of MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3 beta) that requires ATG16L1 but is independent of the ULK1 (unc-51 like autophagy activating kinase 1) and class III phosphatidylinositol 3-kinase (PtdIns3K) complexes. Thermal preconditioning of cells prevented CBK79-induced UPS impairment but failed to restore autophagy, indicating that activation of stress responses does not allow cells to bypass the inhibitory effect of CBK79 on autophagy. The identification of a small molecule that simultaneously impairs the two main proteolytic systems for protein quality control provides a starting point for the development of a novel class of proteostasis-targeting drugs.

Retraction Statement.

Retraction Statement.

A Performance Assessment of Current Formulations of Bare-Wire and Mineral-Insulated-Metal-Sheathed Type N Thermocouples

The Type N thermocouple, at its introduction in the early 1980s, was intended to radically improve base-metal thermocouple measurements and would render other base-metal types obsolete, or so it was claimed. Almost 40 years on, Type K persists in being the thermocouple of choice, despite adequate opportunity for the uptake of Type N. The reasons for this may be many; however, recent research at is showing Type N, at least at low temperatures, is not nearly as stable as early claims made out. This study reports on the inhomogeneities in Type N thermoelements, which develop as a function of temperature and time in a selection of mineral-insulated-metal-sheath (MIMS) and bare-wire samples sourced from a range of manufacturers. Measurements were made using a linear-gradient furnace and high-resolution homogeneity scanner. It was found that Type N thermocouples, in both the bare-wire and MIMS format, are susceptible to significant deviations in Seebeck coefficient from the reference functions at temperatures between 100 °C and 950 °C. In fact, use at temperatures below 500 °C can result in measurement errors equal to or worse than for equivalently specified Type K. Consequently, the benefits of using as-supplied Type N, in terms of accuracy and longevity, are only fully realized at temperatures greater than 900 °C. Despite these findings, additional experiments revealed drift rates can be reduced by about a factor of four if thermal preconditioning between 600 °C and 900 °C is used on MIMS Type N, which is similar to the improvements seen for thermally preconditioned MIMS Type K.

Synthesis of Citrate-Stabilized Silver Nanoparticles Modified by Thermal and pH Preconditioned Tannic Acid.

Silver nanoparticles (AgNPs) may be synthesized by many different methods, with those based on the thermal reduction of silver salts by citric acid or citric acid/tannic acid being amongst the most commonly used. These methods, although widely used and technically simple, can produce particles in which the size, polydispersivity and morphology can vary greatly. In this work nearly mono-dispersed spherical AgNPs have been synthesized via a one-step reduction method by using sodium citrate and varying quantities of Tannic Acid (TA), which was thermally conditioned prior to use in the growth process. It was found that the final size can be further tailored by controlling the amount of TA and the thermal conditioning of the TA at 60 °C at different time points, which changes the size and polydispersivity of AgNPs. To better understand the origin of this effect, optical spectroscopic analysis and 1H NMR of the TA following mild thermal conditioning of the solution have been done. Comparison of thermally conditioned TA and TA exposed to basic pH shows that similar chemical modifications occur and consequently produce similar effects on growth when used in the synthesis of AgNPs. It is proposed that thermal preconditioning of the TA introduces either chemical or structural changes, which decrease the final particle size under a given total silver content.

The influence of supersaturation at low rime accretion rates on thunderstorm electrification from field-independent graupel-ice crystal collisions

Laboratory cloud chamber experiments have revealed the significance of cloud supersaturation on field-independent graupel-ice crystal charging associated with thunderstorm electrification. At rime accretion rates below approximately 1 g m−2 s−1, altering supersaturation can reverse the polarity of graupel charging when other conditions are maintained. Explanations are given to reconcile variation between many published observations by considering the factors associated with particle surface diffusional growth that contribute to the resulting polarity of charge. Findings are consistent with the Relative Diffusional Growth Rate hypothesis. Variations between observations can be qualitatively accounted for by considering the effects of ice crystal thermal preconditioning, crystal size, and cloud supersaturation. The varieties of observed charge polarity reversal as a function of cloud temperature and liquid water content are also characterised. Recommendations are given for future laboratory experimental measurements to avoid ambiguity during interpretation.

Relative Contributions of Packaging Elements to the Thermal Hysteresis of a MEMS Pressure Sensor

Piezoresistive silicon pressure sensor samples were thermally cycled after being consecutively packaged to three different levels. These started with the absolute minimum to allow measurement of the output and with each subsequent level incorporating additional packaging elements within the build. Fitting the data to a mathematical function was necessary both to correct for any testing uncertainties within the pressure and temperature controllers, and to enable the identification and quantification of any hysteresis. Without being subjected to any previous thermal preconditioning, the sensors were characterized over three different temperature ranges and for multiple cycles, in order to determine the relative contributions of each packaging level toward thermal hysteresis. After reaching a stabilised hysteretic behaviour, 88.5% of the thermal hysteresis was determined to be related to the bond pads and wire bonds, which is likely to be due to the large thermal mismatch between the silicon and bond pad metallisation. The fluid-fill and isolation membrane contributed just 7.2% of the total hysteresis and the remaining 4.3% was related to the adhesive used for attachment of the sensing element to the housing. This novel sequential packaging evaluation methodology is independent of sensor design and is useful in identifying those packaging elements contributing the most to hysteresis.

The effect of wetting characteristics, thermophysical properties, and roughness on spray-wall heat transfer in selective catalytic reduction systems

The effects of wettability, thermophysical properties, and roughness on spray-wall heat transfer in automotive selective catalytic reduction (SCR) systems are investigated experimentally. Using static contact angle measurements the wetting characteristics of ferritic and austenitic steel, iron, tungsten, silver, nickel, aluminum oxide, and technical ceramics (Shapal-M, Sialon) are analyzed. Details of the transient spray-wall interaction on the heated material samples (initial wall temperatures 120 ∘C–400 ∘C) are captured with a high-speed camera. The heat transfer from the wall to the impinging spray is calculated from transient temperature fields by using infrared thermography measurements of the plate’s rear side. Our results reveal that the thermal preconditioning of the plate has a significant influence on its wettability, which induces a hysteresis in the spray-wall heat transfer boiling curve. Higher contact angles and higher thermal effusivity have considerable influence on the Leidenfrost temperature. On the contrary, changes in roughness Rz show only a minor effect.

Assessment of an earth-air heat exchanger (EAHE) system for residential buildings in warm-summer Mediterranean climate

Open-loop earth-air heat exchangers (EAHE) can be used as a passive contribution to reduce the energy demand of buildings for heating and cooling, by providing a thermal pre-conditioning of the required ventilation air. This paper aims to numerically assess the influence of three parameters on the overall thermal performance of an EAHE system for residential buildings in warm-summer Mediterranean climate: spacing between pipes, pipes diameter and flowing air velocity. ANSYS-CFX® was used to simulate the EAHE transient behaviour during heating and cooling operation modes, and to evaluate the influence of each parameter on the outlet air temperature and soil-air heat transfer rate. The numerical results were validated against experimental data and compared with previously obtained analytical results. It was concluded that for a certain pipe diameter and distance between adjacent pipes, the higher the air velocity the lower the thermal performance of the system, mainly for cooling. Results also showed that for a certain air velocity and pipe diameter, the distance between pipes can be reduced from 1.0 m to 0.5 m without compromising the EAHE performance, thus allowing a reduction of the land area needed for the EAHE pipes up to ca. 50%.