Heat and Moisture Relevant In Situ Measurements in a Railway Passenger Vehicle Driving through the Swiss Alpine Region

Transportation is a major sector of energy consumption in most, if not in all, European countries. Besides the energy used for traction, energy is also consumed for ventilation, heating, and cooling inside the vehicles to assure traveler comfort. This issue gains increasing importance as the demand for public transport increases in the future. There is a need for retrofit to improve the thermal resistance of the envelope of existing vehicles to reduce the heat loss to the environment during the cold period of the year, especially in the Alpine region. A major concern in adding insulation material to the envelope is the possibility of convective moisture transfer due to air circulation in the vehicle, which would cause condensation accumulation on the cold surfaces. The present investigation addresses this topic by measuring surface and air temperature, air moisture, air flow, and heat flow at several critical locations of a vehicle during its travel in the Swiss Alpine region over several months during the cold period of the year. Temperature measurements showed the potential of reducing the heat losses in some parts of the vehicle. The level and duration of the moisture exposure did not suggest a relevant formation of condensation in the cross-section of the vehicle wall. The observed increase in relative humidity when driving through tunnels is too short to cause relevant condensation in the vehicle shell. The measured low air flow justifies the assumption that no forced convection occurs in the envelope cavities

Thermal conductivity of gypsum plasterboard beyond dehydration and its correlation with the pore structure

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.Gypsum plasterboard is a material used in the building industry for its low weight (porosity 50-65%) and its high resistance to fire due to the endothermic dehydration taking place between 150 and 200°C. Its thermal conductivity which is a decisive thermal property regarding reaction to fire drops by 50% of its initial value after dehydration due to the loss of water (20 mass %) but starts to rise again with rising temperature and reaches its initial value around 750°C. The present study shows that this rise is not due to the increasing radiative or conductive heat transfer but to changes in the bimodal pore structure which leaves the overall structural dimensions nearly unchanged (dilatation of around 2%). Different methods such as mercury intrusion porosimetry, scanning electron microscopy and in-situ X-ray diffraction up to 1000°C were carried out to investigate the correlation between pore structure and thermal conductivity of this material.dc201

Fire performance of phase change material enhanced plasterboard

Sustainable construction materials are increasingly being used to reduce the carbon footprint of modern buildings. These materials have the potential to change the fire dynamics of compartments by altering the compartment energy balance however there is little quantitative understanding of how these materials behave in the event of a real fire. The changes in fire dynamics may be due to increased fuel load in a compartment, reduced time to failure or promotion of flame spread. The objective of this research is to quantify how Phase Change Materials (PCMs) perform in realistic fire scenarios. It was found that a plasterboard product containing microencapsulated PCMs will behave similarly to a charring solid and have the potential to contribute significant fuel to a compartment fire but that they maintain integrity for the duration of flaming period. The critical heat flux for this product was determined in the cone calorimeter to be 17.5 ± 2.5 kW m−2, the peak heat release rate and mass loss rate ranged from 60.2 kW m−2 to 107 kW m−2 and 1.88 g s−1 m−2 to 8.47 g s−1 m−2 respectively for exposures between 20 kW m−2 and 70 kW m−2. Sample orientation was found to increase the peak heat release rate by up to 25%, whilst having little to no effect on the mass loss rate. These parameters, in addition to the in-depth temperature evolution and ignition properties, can be used as design criteria for balancing energy savings with quantified fire performance

Experimental and numerical investigation of the thermal performance of a protected vacuum-insulation system applied to a concrete wall

A concrete wall externally insulated with six expanded polystyrene boards, each containing three vacuum insulation panels, was investigated both experimentally and numerically. The main goal of this study was to determine the thermal performance of vacuum-insulation panels applied to walls in building constructions. Comparisons were made with conventional insulation and also with systems including damaged, i.e., vented vacuum panels. Since the vacuum insulation panels are encased in a metallized laminates as barriers against permeation of moisture and gas, special attention was given to the edge effects. Stepwise adjustment of the measured and calculated results reported here provide a general assessment of the efficacy of this insulation system applied on different wall materials. A functional representation of the measured data, for steady-state conditions, is introduced. Moreover, infrared thermography was used to confirm the three dimensionally calculated temperature distributions on the surface. The present investigation was part of the research programme "High Performance Thermal Insulation in Buildings and Building Systems" of the international energy agency (IEA).Highly insulated walls Vacuum-insulation panels Edge effect Linear thermal transmittance U-value Guarded hot-box

Evaluation of Three Different Retrofit Solutions Applied to the Internal Surface of a Protected Cavity Wall

AbstractA south-east oriented façade of a protected building of Politecnico di Milano has been retrofitted on its inner surface with respect to energy consumption and thermal comfort. Three prototype solutions including special perlite boards and aerogel composite materials have been used. The wall has been monitored by a wireless system of temperature, moisture and heat flux sensors before and after retrofit for about 6 months each. The acquired data enabled the determination and transient behaviour of hygro-thermal properties of the investigated façade before and after retrofitting using the average method. Measured results were compared to those obtained from thermo-hygric simulations

Ug-value and edge heat loss of triple glazed insulating glass units: A comparison between measured and declared values

Triple glazed low-e coated insulating glass units with argon filling of five different suppliers on the European market with a declared thermal transmittance in the undisturbed centre of glass (Ug-value) of 0.6 W/m2K have been purchased from resellers and tested in a guarded hot plate at vertical position. The measured results showed deviations towards higher values for all 5 types. These have been analysed by recurring to the determination of the two main factors namely the gas mixture in the two cavities and the emissivity of the coated glass panes. Nondestructive measuring methods for gas mixture analysis and standardized calculation methods for the Ug-value have been used to analyse the influence of these two factors. In a further step the edge heat loss due to the spacer of the insulating glass units has been measured by using two “halves” of each glazing type with a double edge running through the middle of the measured sample. This was done following a standardized test method for the determination of the edge heat loss of Vacuum Insulation Panels (VIP). Finally, pieces of the coated glass panes were cut out of the glazing units and their emissivity measured with both an infrared spectrometer and an emissiometer. Results showed an increased emissivity value for the coated surfaces leading to higher Ug values than measured. This is partly due to the exposure to air and the possible degradation of the coating. The investigation shows non-destructive emissivity determination is needed to get more accurate in-situ emissivity values of the coatings