Redistribution Of Heat Research Articles

Quantifying 3D building form effects on urban land surface temperature and modeling seasonal correlation patterns

Multiple factors regulate urban land surface temperature (LST), including land cover, climate, and urban form, among which urban form is now receiving more and more attention. Some studies have discussed the planar effects of urban form on LST, whereas less concern has been devoted to the vertical structure of urban areas, which can have a significant effect on heat redistribution. In this paper, we quantify the three-dimensional building form (3DBF) effects on LST captured by Landsat thermal sensors over four seasons by using a random forest (RF) regression method. The five 3DBF factors of building density (BD), building height (BH), sky view factor (SVF), frontal area index (FAI), and building shadow (BS) are calculated within a grid. The seasonal correlation of the 3DBF factors with LST is analyzed, and seven correlation patterns are modeled for the city of Wuhan in China. The results show that: 1) The best grid scale for the building form analysis in a city such as Wuhan is 180 m. 2) The 3DBF factors have a significant effect on urban LST over the four seasons. BD, BH and BS are the season-stable factors, among which BD has a heating effect, which reaches a maximum of 3.6 °C in spring, while BS has a cooling effect, which reaches −3.4 °C in winter. There is also a transition point for BH between heating and cooling at a height of 10 m. 3) SVF and FAI are season-varying factors, in which SVF has cooling effect, except in summer, while FAI also has a cooling effect, but not in winter. These findings will help us to understand how building form affects urban surface temperature, and will provide a reference for urban policy makers and planners in the future.

Global heat balance and heat uptake in potential temperature coordinates

The representation of ocean heat uptake in Simple Climate Models used for policy advice on climate change mitigation strategies is often based on variants of the one-dimensional Vertical Advection/Diffusion equation (VAD) for some averaged form of potential temperature. In such models, the effective advection and turbulent diffusion are usually tuned to emulate the behaviour of a given target climate model. However, because the statistical nature of such a “behavioural” calibration usually obscures the exact dependence of the effective diffusion and advection on the actual physical processes responsible for ocean heat uptake, it is difficult to understand its limitations and how to go about improving VADs. This paper proposes a physical calibration of the VAD that aims to provide explicit traceability of effective diffusion and advection to the processes responsible for ocean heat uptake. This construction relies on the coarse-graining of the full three-dimensional advection diffusion for potential temperature using potential temperature coordinates. The main advantage of this formulation is that the temporal evolution of the reference temperature profile is entirely due to the competition between effective diffusivity that is always positive definite, and the water mass transformation taking place at the surface, as in classical water mass analyses literature. These quantities are evaluated in numerical simulations of present day climate and global warming experiments. In this framework, the heat uptake in the global warming experiment is attributed to the increase of surface heat flux at low latitudes, its decrease at high latitudes and to the redistribution of heat toward cold temperatures made by diffusive flux.

Distinct sources of interannual subtropical and subpolar Atlantic overturning variability

The Atlantic meridional overturning circulation (AMOC) is pivotal for regional and global climate due to its key role in the uptake and redistribution of heat and carbon. Establishing the causes of historical variability in AMOC strength on different timescales can tell us how the circulation may respond to natural and anthropogenic changes at the ocean surface. However, understanding observed AMOC variability is challenging because the circulation is influenced by multiple factors that co-vary and whose overlapping impacts persist for years. Here we reconstruct and unambiguously attribute intermonthly and interannual AMOC variability at two observational arrays to the recent history of surface wind stress, temperature and salinity. We use a state-of-the-art technique that computes space- and time-varying sensitivity patterns of the AMOC strength with respect to multiple surface properties from a numerical ocean circulation model constrained by observations. While, on interannual timescales, AMOC variability at 26° N is overwhelmingly dominated by a linear response to local wind stress, overturning variability at subpolar latitudes is generated by the combined effects of wind stress and surface buoyancy anomalies. Our analysis provides a quantitative attribution of subpolar AMOC variability to temperature, salinity and wind anomalies at the ocean surface.

Lateral redistribution of heat and salt in the Nordic Seas

The locations, times, and mechanisms by which heat and salt are transported through and within the Nordic Seas are discussed. The analysis is based on a regional, high resolution coupled sea ice-ocean numerical model, a climatological hydrographic data set, and atmospheric reanalysis. The model and climatology are broadly consistent in terms of heat loss, water masses, and mean geostrophic currents. The model fields are used to demonstrate that the dominant exchange between basins is an export of warm, salty water from the Norwegian Sea into the Greenland and Iceland Seas, with both the mean cyclonic boundary current system and eddy fluxes playing important roles. In both the model and the climatology, approximately 2/3 of the heat loss to the atmosphere over the Nordic Seas is found over the mean cyclonic flow and 1/3 takes place within the closed recirculations in the interior of each of the basin gyres, with the Norwegian Sea having the largest heat loss. The seasonal cycle is dominated by local air-sea heat flux within the gyres while it is dominated by lateral advection in the cyclonic boundary current, particularly in the northern Norwegian and Greenland Seas. The freshwater flux off the east Greenland shelf is correlated with the local winds such that in winter, when winds are generally towards the southwest, freshwater is advected onto the shelf and in summer, when winds are weak or towards the northeast, freshwater is advected into the Greenland Sea, which leads to salinification in winter and freshening in summer.

The effects of historical ozone changes on Southern Ocean heat uptake and storage

Atmospheric ozone concentrations have dramatically changed in the last five decades of past century. Herein we explore the effects of historical ozone changes that include stratospheric ozone depletion on Southern Ocean heat uptake and storage, by comparing CESM1 large ensemble simulations with fixed-ozone experiment. During 1958–2005, the ozone changes contribute to about 50% of poleward intensification of the Southern Hemisphere westerly winds in historical simulations, which intensifies the Deacon Cell and residual meridional overturning circulation, thus contributing to heat redistribution in the Southern Ocean. Heat budget analysis shows that, in response to historical ozone changes, heat is taken up between 50 and 58 °S mainly through changes in sensible heat flux, shortwave radiation flux, and the flux due to seasonal sea ice formation and melt. A major part of the absorbed heat, however, is redistributed equatorward primarily through Eulerian mean ocean heat transport such that ocean heat storage peaks at lower latitudes, around 44 °S. The ozone-induced interior warming contributes to about 22% of the historical Southern Ocean warming over 1958–2005. Poleward of 62 °S where a subsurface temperature inversion occurs, shoaling isopycnals lead to warming and salinification in the upper ocean. To the north of 50 °S, the deep-reaching warming and freshening that correspond to the ocean heat storage maximum are primarily set by the deepening of isopycnals. The large-scale patterns of isopycnal shoaling (deepening) at high (middle) latitudes are consistent with the overlying negative (positive) wind stress curl anomalies related to the poleward intensification of westerly winds, suggesting that the wind changes play an important role in the Southern Ocean heat redistribution under the ozone forcing.

Pseudo-2D modelling of heat redistribution through H2 thermal dissociation/recombination: consequences for ultra-hot Jupiters

ABSTRACT Thermal dissociation and recombination of molecular hydrogen, H2, in the atmospheres of ultra-hot Jupiters (UHJs) has been shown to play an important role in global heat redistribution. This, in turn, significantly impacts their planetary emission, yet only limited investigations on the atmospheric effects have so far been conducted. Here, we investigate the heat redistribution caused by this dissociation/recombination reaction, alongside feedback mechanisms between the atmospheric chemistry and radiative transfer, for a planetary and stellar configuration typical of UHJs. To do this, we have developed a time-dependent pseudo-2D model, including a treatment of time-independent equilibrium chemical effects. As a result of the reaction heat redistribution, we find temperature changes of up to ∼400 K in the atmosphere. When TiO and VO are additionally considered as opacity sources, these changes in temperature increase to over ∼800 K in some areas. This heat redistribution is found to significantly shift the region of peak atmospheric temperature, or hotspot, towards the evening terminator in both cases. The impact of varying the longitudinal wind speed on the reaction heat redistribution is also investigated. When excluding TiO/VO, increased wind speeds are shown to increase the impact of the reaction heat redistribution up to a threshold wind speed. When including TiO/VO there is no apparent wind speed threshold, due to thermal stabilization by these species. We also construct pseudo-2D phase curves from our model, and highlight both significant spectral flux damping and increased phase offset caused by the reaction heat redistribution.

Regional Asymmetries in Ocean Heat and Carbon Storage due to Dynamic Redistribution in Climate Model Projections

AbstractProjected changes in ocean heat and carbon storage are assessed in terms of the added and redistributed tracer using a transport-based framework, which is applied to an idealized climate model and a suite of six CMIP5 Earth system models following an annual 1% rise in atmospheric CO2. Heat and carbon budgets for the added and redistributed tracer are used to explain opposing regional patterns in the storage of ocean heat and carbon anomalies, such as in the tropics and subpolar North Atlantic, and the relatively reduced storage within the Southern Ocean. Here the added tracer takes account of the net tracer source and the advection of the added tracer by the circulation, while the redistributed tracer takes account of the time-varying circulation advecting the preindustrial tracer distribution. The added heat and carbon often have a similar sign to each other with the net source usually acting to supply the tracer. In contrast, the redistributed heat and carbon consistently have an opposing sign to each other due to the opposing gradients in the preindustrial temperature and carbon. These different signs in heat and carbon redistribution can lead to regional asymmetries in the climate-driven changes in ocean heat and carbon storage. For a weakening in the Atlantic overturning and strengthening in the Southern Ocean residual circulation, the high latitudes are expected to have heat anomalies of variable sign and carbon anomalies of a consistently positive sign, since added and redistributed tracers are opposing in sign for heat and the same sign for carbon there.

Heat flow redistribution in wall structure during diurnal cycle in summer

The standardized indicator is the heat transfer resistance as the main factor that plays the main role in assessing the energy efficiency of the thermal envelope of a building. During the last decades, the climatic conditions change toward the increase in average daily temperature in the summer period. Thus, the thermal resistance of external wall structures becomes more and more urgent. This problem is reduced to an assumption that the heat flow in the wall structure is directed from the external surface to the internal. This paper analyzes the heat flow distribution and redistribution in time in the wall structure. The paper presents a comparative analysis of the modelling and calculation results of the nonstationary heat flow for solving the thermal stability problem.

Sea Surface Temperatures in the Indian Sub‐Antarctic Southern Ocean for the Last Four Interglacial Periods

AbstractInterglacial periods (IG) offer an opportunity to understand natural climate variability and its drivers under potential warmer‐than‐present conditions. However, sea‐surface temperature (SST) records from the Southern Ocean (SO) are limited. The first SST record from the Sub‐Antarctic western Indian SO covering the last four IGs suggest warmer conditions during Marine Isotope Stage 5e than 9e, 7e, and Holocene. Each IG presents two (early and late) warm phases interrupted by a cooling, except Holocene that experienced a continuous warming. The early warm phase might be attributable to changes in northern summer insolation with feedbacks from Northern and Southern Hemisphere ice‐sheets, global oceanic circulation, and the carbon cycle. Conversely, the late warm phase might be due to changes in Southern Hemisphere summer insolation. Larger millennial‐scale SST variability for IGs older than Holocene could be attributed to a less stable thermohaline circulation, which resulted in more variable heat redistribution between the two hemispheres.

Correlation between the Perfusion Index and Intraoperative Hypothermia: A Prospective Observational Pilot Study.

Background and Objectives: We examined the association between the baseline perfusion index (PI) and changes in intraoperative body temperature during general anesthesia. The PI reflects the peripheral perfusion state. The PI may be associated with changes in body temperature during general anesthesia because the degree of redistribution of body heat from the central to the peripheral compartment varies depending on the peripheral perfusion state. Materials and Methods: Thirty-eight patients who underwent brain surgery were enrolled in this study. The baseline PI and body temperature of the patients were measured on entering the operating room. Body temperature was recorded every 15 min after induction of anesthesia using an esophageal temperature probe. Univariate and multivariate logistic regression analyses were performed to identify the risk factors for intraoperative hypothermia. Results: Eighteen patients (47 %) developed hypothermia intraoperatively. The baseline PI was significantly lower among patients in the hypothermia group (1.8 ± 0.7) than among those in the normothermia group (3.0 ± 1.2) (P < 0.001). The baseline PI and body temperature were independently associated with intraoperative hypothermia (PI: odds ratio [OR], 0.270; 95% confidence interval [CI], 0.105–0.697; P = 0.007, baseline body temperature: OR, 0.061; 95% CI, 0.005–0.743; P = 0.028). Conclusions: This study showed that low baseline PI was the factor most related to the development of intraoperative hypothermia. Future studies should consider the PI as a predictor of intraoperative hypothermia.

Effectiveness of prewarming in prevention of inadvertent intraoperative hypothermia

Background: Inadvertent perioperative hypothermia (IPH), defined as a perioperative core temperature < 36 °C is attributable to redistribution of body heat from the core to peripheries during the initial phase of anaesthesia and is difficult to treat. We conducted this study to find the effectiveness of pre-warming in preventing the occurrence of hypothermia intraoperatively in adult patients undergoing elective laparotomy under general anaesthesia. Material and Methods: Forty-four adult patients undergoing elective laparotomy were randomized into two groups of 22 each. Patients in Group P were prewarmed for 60 minutes prior to induction and those in Group C did not receive prewarming. Results: Patients in Group P had a significantly higher peripheral temperature at induction compared to those in Group C (p = 0.025), whereas the core temperature at induction was found to be comparable between the 2 groups. The core to peripheral temperature gradient was found to be lower in group P when compared to group C and the difference was statistically significant (p = 0.042). The core temperature dropped to less than 35 °C in the first two hours following induction in 2 patients in Group P and in 14 patients in group C (p < 0.001). The rate of drop in the core temperature was higher in group C compared to group P (p=0.002).The mean peripheral temperature as well as the core temperature in group P was significantly higher than in group C from induction to 60th minute, and it was statistically significant. Conclusion: In the first 2 hours post induction, prewarming is effective in preventing the drop in core temperature and reduces the rate of drop in core temperature. Prewarming is effective in reducing the core to peripheral temperature gradient at induction.

Synergy of In Situ and Satellite Ocean Observations in Determining Meridional Heat Transport in the Atlantic Ocean

AbstractThe meridional overturning circulation (MOC) is a major driver in global redistribution of heat, which modulates global climate and weather. Altimeter sea surface height measurements and in situ hydrographic data are combined in this work to derive monthly synthetic temperature and salinity (T/S) profiles along zonal transbasin sections in both the North (26.5°N) and South (20°S, 25°S, 30°S, and 35°S) Atlantic Ocean since 1993, which are then used to estimate the MOC and meridional heat transport (MHT). Consistent with previous studies, the results indicate that the MHT is highly correlated with the MOC at all five latitudes. At 26.5°N the mean MHT from synthetic profiles (1.09 ± 0.21 PW) is slightly lower than that from the RAPID‐MOCHA‐WBTS array (1.20 ± 0.28 PW), but their interannual variabilities show good agreements. Both the geostrophic and Ekman components contribute significantly to the MHT variability, with the geostrophic component dominating during 1993–2004 and the Ekman component dominating during 2005–2014. In the South Atlantic, the MHT seasonal cycle strengthens southward from 20°S to 34.5°S. On interannual time scale, the MHT at 20°S and 25°S experiences larger variations than that at 30°S and 34.5°S, in part due to the fact that the geostrophic and Ekman components work together to strengthen the MHT changes, while they tend to work against each other at 30°S and 34.5°S. Results shown here suggest that integrating data from different observing platforms provides better means to estimate the MOC and MHT in near real time.

Unbalanced exchange flow and its implications for the night cooling of buildings by displacement ventilation

Passive ventilation of buildings at night forms an essential part of a low-energy cooling strategy, enabling excess heat that has accumulated during the day to self-purge and be replaced with cooler night air. Instrumental to the success of a purge are the locations and areas of ventilation openings, and openings positioned at low and at high levels are a common choice as there is then the expectation that a buoyancy-driven displacement flow will establish and persist. Desirable for their efficiency, displacement flows guide excess heat out through high-level openings and cooler air in through low-level openings. Herein we show that displacement flow cannot be maintained for the full duration of a purge. Instead, the flow must transition to an ‘unbalanced exchange flow’, whereby the cool inflow of air at low level is maintained but there is now a warm outflow and a cool inflow occurring simultaneously at the high-level opening. The internal redistribution of heat caused by this exchange alters the rate at which heat is self-purged and the time thought necessary to complete a purge. We develop a theoretical model that captures and predicts these behaviours. Our approach is distinct from all others which assume that a displacement flow will persist throughout the purge. Based on this enhanced understanding, and specifically that the transition to unbalanced exchange flow changes the rate of cooling and resultant emptying times, we anticipate that practitioners will be better placed to design passive systems that meet their target specifications for cooling.

Flow of Devonian anatectic crust in the accretionary Altai Orogenic Belt, central Asia: Insights into horizontal and vertical magma transfer

AbstractFlow of partially molten crust is a key contributor to mass and heat redistribution within orogenic systems, however, this process has not yet been fully understood in accretionary orogens. This issue is addressed in a Devonian migmatite-granite complex from the Chinese Altai through structural, petrological, and geochronological investigations presented in this study. The migmatite-granite complex records a gradual evolution from metatexite, diatexite to granite and preserves a record of two main Devonian phases of deformation designated D1 and D2. The D1 phase was subdivided into an early crustal thickening episode (D1B) and a later extensional episode (D1M) followed by D2 upright folding. The D1M episode is associated with anatexis in the deep crust. Vertical shortening, associated with D1M, gave rise to the segregation of melt and formation of a sub-horizontal layering of stromatic metatexite. This fabric was reworked by the D2 deformation associated with the migration of anatectic magma in the cores of F2 antiforms. Geochronological investigations combined with petro-structural analysis reveal that: (1) D1M partial melting started probably at 420–410 Ma and formed sub-horizontal stromatic metatexites at ∼30 km depth; (2) The anatectic magma accumulated and migrated when a drainage network developed, as attested by the pervasive formation of massive diatexite migmatites, at 410–400 Ma; (3) Soon after, massive flow of the partially molten crust from orogenic lower to orogenic upper crustal levels, assisted by the interplay between D2 upright folding and magma diapirism, led to migmatite-granite emplacement in the cores of regional F2 antiforms that lasted until at least 390 Ma; (4) a terminal stage was manifested by the emplacement of 370–360 Ma granite dykes into the surrounding metamorphic envelope. We propose that Devonian anatexis assisted by deformation governed first the horizontal and then the vertical flow of partially molten orogenic lower crust, which drove crustal flow, mass redistribution, and crustal differentiation in the accretionary system of the Chinese Altai.

Contribution of Ocean Physics and Dynamics at Different Scales to Heat Uptake in Low-Resolution AOGCMs

AbstractUsing an ensemble of atmosphere–ocean general circulation models (AOGCMs) in an idealized climate change experiment, this study quantifies the contributions to ocean heat uptake (OHU) from ocean physical parameterizations and resolved dynamical processes operating at different scales. Analysis of heat budget diagnostics reveals a leading-order global heat balance in the subsurface upper ocean in a steady state between the large-scale circulation warming it and mesoscale processes cooling it, and shows that there are positive contributions from processes on all scales to the subsurface OHU during climate change. There is better agreement among the AOGCMs in the net OHU than in the individual scales/processes contributing to it. In the upper ocean and at high latitudes, OHU is dominated by small-scale diapycnal processes. Below 400 m, OHU is dominated by the superresidual transport, representing large-scale ocean dynamics combined with all parameterized mesoscale and submesoscale eddy effects. Weakening of the AMOC leads to less heat convergence in the subpolar North Atlantic and less heat divergence at lower latitudes, with a small overall effect on the net Atlantic heat content. At low latitudes, the dominance of advective heat redistribution is contrary to the diffusive OHU mechanism assumed by the commonly used upwelling-diffusion model. Using a density water-mass framework, it is found that most of the OHU occurs along isopycnal directions. This feature of OHU is used to accurately reconstruct the global vertical ocean warming profile from the surface heat flux anomalies, supporting advective (rather than diffusive) models of OHU and sea level rise.

Multi-decadal trends in Antarctic sea-ice extent driven by ENSO–SAM over the last 2,000 years

Antarctic sea ice has paradoxically become more extensive over the past four decades despite a warming climate. The regional expression of this trend has been linked to changes in vertical redistribution of ocean heat and large-scale wind-field shifts. However, the short length of modern observations has hindered attempts to attribute this trend to anthropogenic forcing or natural variability. Here, we present two new decadal-resolution records of sea ice and sea surface temperatures that document pervasive regional climate heterogeneity in Indian Antarctic sea-ice cover over the last 2,000 years. Data assimilation of our marine records in a climate model suggests that the reconstructed dichotomous regional conditions were driven by the multi-decadal variability of the El Nino Southern Oscillation and Southern Annular Mode (SAM). For example, during an El Nino/SAM– combination, the northward sea-ice transport was reduced while heat advection from the subtropics to the Southern Ocean increased, which resulted in reduced sea-ice extent in the Indian sector as sea ice was compacted along the Antarctic coast. Our results therefore indicate that natural variability is large in the Southern Ocean and suggest that it has played a crucial role in the recent sea-ice trends and their decadal variability in this region. Common Era sea-ice variability in the Indian sector of the Southern Ocean was strongly influenced by interacting climate modes, according to climate modelling and an analysis of sea-ice and temperature proxies.

Heat source model for electron beam welding of nickel-based superalloys

Abstract An adapted heat source model is developed for transient thermal numerical analysis of electron beam welded nickel-based alloy with increased susceptibility to hot cracking. The model enables the consideration of heat redistribution due to beam deflection phenomena. The modeling concept is validated by the appropriate theoretical models and in addition, experimental studies especially performed for this purpose. Special attention is given to the calibration of heat source model parameters. The calibration procedure is based on a statistical approach involving a combination of novel analytical solutions and quasi-steady state finite element models. The model parameter field is statistically analyzed, and a prediction algorithm is developed using optimization algorithms from the six sigma theory. The reliability and practicability of the model is demonstrated by validation weldments. The work is dedicated to precisely calculating the temperature field in the high temperature region around the weld pool and thus to provide a more detailed explanation of the formation of hot cracks when welding turbine materials commonly used in industry and aircraft constructions.

Experimental Study of Temperature Distribution in a Cyclone-Vortex Furnace

This article describes the experience and results of experimental study of the temperature distribution in the refractory lining of the gas and liquid fuel cyclone-vortex furnace (CVF). Temperatures were measured with type K thermocouples. Most of the thermocouples are located a depth of 25 mm from the surface combustion chamber. With increasing boiler load observed decrease in temperature and increase of plating unevenness of the temperature distribution in the combustion chamber. This is due to the redistribution of heat generated between the combustion chamber and the firebox as the load increases. The results of heat transfer studies in CVF will lead to a reduction in the thickness of the lining, modernization of the CVF structure. In the future, abandon the use of refractory lining in CVF

Formation and dynamics of water clouds on temperate sub-Neptunes: the example of K2-18b

Context. Hubble Space Telescope (HST) spectroscopic transit observations of the temperate sub-Neptune K2-18b were interpreted as the presence of water vapour with potential water clouds. 1D modelling studies also predict the formation of water clouds in K2-18b’s atmosphere in some conditions. However, such models cannot predict the cloud cover, which is driven by atmospheric dynamics and thermal contrasts, and thus neither can they predict the real impact of clouds on spectra. Aims. The main goal of this study is to understand the formation, distribution, and observational consequences of water clouds on K2-18b and other temperate sub-Neptunes. Methods. We simulated the atmospheric dynamics, water cloud formation, and spectra of K2-18b for a H2-dominated atmosphere using a 3D general circulation model. We analysed the impact of atmospheric composition (with metallicity from 1× solar to 1000× solar), concentration of cloud condensation nuclei, and planetary rotation rate. Results. Assuming that K2-18b has a synchronous rotation, we show that the atmospheric circulation in the upper atmosphere essentially corresponds to a symmetric day-to-night circulation with very efficient heat redistribution. This regime preferentially leads to cloud formation at the sub-stellar point or at the terminator. Clouds form at metallicity ≥100× solar with relatively large particles (radius = 30–450 μm). At 100–300× solar metallicity, the cloud fraction at the terminators is small with a limited impact on transit spectra. At 1000× solar metallicity, very thick clouds form at the terminator, greatly flattening the transit spectrum. The cloud distribution appears very sensitive to the concentration of cloud condensation nuclei and to the planetary rotation rate, although the impact on transit spectra is modest in the near-infrared. Fitting HST transit data with our simulated spectra suggests a metallicity of ~100–300× solar, which is consistent with the mass-metallicity trend of giant planets in the Solar System. In addition, we found that the cloud fraction at the terminator can be highly variable in some conditions, leading to a potential variability in transit spectra that is correlated with spectral windows. This effect could be common on cloudy exoplanets and could be detectable with multiple transit observations. Finally, the complex cloud dynamics revealed in this study highlight the inherent 3D nature of clouds shaped by couplings between microphysics, radiation, and atmospheric circulation.

Estimation of energy-saving potential and indoor thermal comfort by the central control of the heating curve in old apartment buildings

In this research, an existing building calibrated simulation model from 1981 was built based on measured energy and indoor temperature data. The model was used to study the central control's energy-saving potential. With parametric simulations, DHW circulation internal heat gain and ventilation airflow rate was determined as 85% and 0.29 l/s/m², respectively. DHW circulation heat loss has been found almost as high as DHW use. Dropping the heating curve from 70/40 °C to 65/35 °C resulted in a saving of 0.6 kWh/m²a (0.8% of space heating energy) on the cost of thermal comfort as yearly hours of the mean air temperature below 21 °C rose from 2.7% to 9.0%. It was necessary to reduce the heating curve to 55/25 °C in a hypothetical scenario with fully open thermostats, indicating heat redistribution from warmer to colder rooms, leading to higher heating energy. The findings indicate no energy saving potential due to compromising thermal comfort even by 5 °C heating curve reduction. It was revealed that the building average indoor temperature is not a factor to estimate energy-saving potential because of too low temperature in the coldest apartments.