Calculation of Building Heat Losses through Slab-on-Ground Structures Based on Soil Temperature Measured In Situ

The earth-to-air heat exchanger (EAHE) is a well-founded and verified solution used in modern buildings both for heating and cooling purposes around the world. However, there is a lack of studies on operation of such devices cooperating with ventilation systems of buildings in hourly time step. In this study, the 5R1C thermal network model of a building from EN ISO 13790 was coupled with the EAHE model from EN 16798-5-1 to calculate hourly outlet air temperature. To improve the effectiveness of the considered solution, an additional algorithm was developed to choose between the EAHE outlet and ambient air as the source of ventilation air. Simulations were conducted in a spreadsheet for a low-energy single-family building. Ground temperature was compared with measurements taken in the considered location. The application of the EAHE with the proposed bypass resulted in a decrease in annual energy use for space heating and cooling from 14.82 GJ and 1.67 GJ to 12.74 GJ and 0.93 GJ, i.e., by 14% and 44%, respectively. Peak hourly heating and cooling thermal power decreased from 2.73 kW and 3.06 kW to 2.21 kW and 2.34 kW. Introduction of a bypass and switching between the EAHE and ambient air as the source of ventilation for the building resulted in annual energy savings of 123 kWh.

Section: Ground Temperaturementioning

confidence: 99%

Hourly Simulation of an Earth-to-Air Heat Exchanger in a Low-Energy Residential Building

Michalak

2022

“…Several factors influence ground temperature. These include soil volumetric heat capacity, thermal conductivity, latent heat, changes in ambient temperature, and the characteristics of the ground surface, such as vegetation and slope [8]. The amplitude of daily average solar radiation flux (amount of solar power radiated through a given area in the form of photons or other particles) affects the total amount of heat transferred between the environment and the sub-soil where the building is located [9].…”

Section: Literature Review 121 Factors That Influence Heat Losses Fro...mentioning

confidence: 99%

“…The temperature of the ground surface is affected by several factors, including energy loss by evaporation, heat transfer between the ground surface and deeper layers, convection, and radiation both in the immediate and farther surroundings. However, the temperature of the ground at any given point (on surface or beneath) depends also on the depth of the point beneath the ground surface, which yields surface temperatures (for points on or immediately beneath the surface), sub-surface temperatures (for points beneath the surface but in the shallow zone), and deep surface temperatures (for points beneath the surface but in the deep zone) [8]. Research by the authors of [10] shows that the factors influencing temperatures for surface, sub-surface, and deep surface zones significantly differ.…”

Section: Literature Review 121 Factors That Influence Heat Losses Fro...mentioning

confidence: 99%

Relative Comparison of Benefits of Floor Slab Insulation Methods, Using Polyiso and Extruded Polystyrene Materials in South Africa, Subject to the New National Building Energy Efficiency Standards

Kabundu,

Mbanga,

Botha

et al. 2024

This article aims to assess the benefits of floor slab insulation measures using extruded polystyrene (XPS) and polyisocyanurate (also referred to as polyiso or PIR) insulation materials at various levels of insulation thicknesses for a detached residential building. An EnergyPlus simulation analysis was carried out within the seven energy zones (represented by eight locations) of South Africa in accordance with the South African national code for building energy efficiency (SANS10400-XA). The energy savings and payback periods related to the use of the insulation over a lifecycle period of 50 years were assessed. Cape Town (zone 4) behaved differently from other locations and hardly benefited from the application of floor slab insulation measures. Generally, polyiso (PIR) insulation performed better than XPS for vertical gap insulation, and lower insulation thicknesses required higher insulation depths to maximize energy savings. Similarly, lower insulation thicknesses (25 mm and 50 mm) required higher perimeter insulation widths to maximize energy savings for horizontal perimeter insulation, especially in Sutherland (zone 6) and Cape Town. The maximization of energy savings was also achieved at low insulation thickness for the full floor slab insulation method, except for Sutherland and Fraserburg (zone 7). The locations that benefitted most from the floor slab insulation methods were Pretoria (zone 5), Thohoyandou (zone 3), Sutherland (zone 6), Fraserburg (zone 7), Welkom (zone 1), Ixopo (zone 5H), Witbank (zone 2), and Cape Town (zone 4), in that order. Generally, higher net energy savings are achieved in areas with lower humidity levels and areas with greater annual sums of both cooling and heating degree days.

“…Modelling heat and fluid flows as well as thermal-, flow-, and strength-related processes plays an important role in the design and operation in engineering. The influence of the real ground temperature on a building's heat loss is analysed in [1]. The numerical model of heating and cooling unit with a reversible heat pump based on CO 2 is presented in [2].…”

Section: Introductionmentioning

confidence: 99%

“…(3,1), (62, 1), and (191, 1). A reduction in the time step to Δt = 10 s involved a slight difference in the temperature transients.…”

mentioning

confidence: 99%

An Iterative Algorithm for the Estimation of Thermal Boundary Conditions Varying in Both Time and Space

Duda

Konieczny

2022

The presented survey of the up-to-date state of knowledge indicates that despite the great number of works devoted to the issue in question, there is no simple method that allows the use of commercial programs for the identification of the transient thermal state in elements with a simple or complex shape. This paper presents an inverse method developed to estimate the convective heat transfer coefficient varying both in time and space on a vertical plate during its cooling. Despite the smaller number of measurement points and larger disturbance of measured temperatures compared to the data presented in the available literature, comparable results are obtained. The developed iterative algorithm is also applied to estimate the time- and space-dependent heat flux and the convective heat transfer coefficient in the steam boiler membrane waterwall. The analysed component has the form of the non-simply connected and complex shape domain Ω. Temperature-dependent thermophysical properties are used. Calculations are performed for the unknown heat flux or heat transfer coefficient distribution on the domain boundary based on measured temperature transients disturbed with a random error of 0.5 °C. To reduce oscillations, the number of future time steps of NF = 20 is selected. The number of iterations in each time step ranges between 1 and 8. The estimated boundary conditions are close to the exact values. In this work, the ANSYS software using the FEM is applied.