Fire around storage tanks for petroleum products can have disastrous consequences for the environment and the population. These fires, due to accident or arson, are very well managed by security ...divisions but, nevertheless, involve the release of an amount of vapour from the petroleum present in the storage device. The exposure of a non-refrigerated aboveground liquid petroleum or petroleum product storage tank to fire can also lead to internal overpressure. PV-valves ensure that the normal and emergency venting requirements are satisfied, and determination of such requirements is key for the safety of petroleum tanks and should not be underestimated. This paper presents and discusses some methods that can be used to evaluate the vapour flow. In the aim of finding an exact answer rapidly, a thermal analytical approach is first investigated, which reveals the complexity of the solution. Thus, a numerical approach, based on finite-volume description, is used to set the first steps of the flow assessment. Based on a thermodynamic hypothesis, a simplified method is finally put forward for the evaluation of the amount of vapour released. The algorithm used to determine how temperature, pressure and flow evolve over time, which is very useful information for the safety of these devices, is then detailed and the results discussed.
Nowadays, with the improvement of living standards, air-conditioning systems have been widely used causing more health problems linked to air-conditioning systems and indoor air quality. When an air ...handling unit is designed for a conference room, its variable use demands an outdoor air rate control in particular to optimize energy consumption of the new air heating/cooling. Based on an experimental site, the present work shows how to combine air quality and the improvement of energy consumption thanks to a way to define a control strategy. The control problem considered here is the management of air quality associated to a control of the outdoor air rates. A review of classical tuning methods is led in order to select suitable ones. Thus, a linearization of the phenomena must be done to border the system expression in tuning methods. Several classical methods are studied and the family model is chosen: monovariable and multivariable applications are brought to fruition. Simulations and applications permit to enhance energy consumption through the choice of a strict way to tune such control equipments.
•Critical analysis of various tools used for commissioning in buildings.•Evaluation of these tools in the considered commissioning phases.•Evaluation of their operability, potential (fault detection, ...energy savings evaluation), and results.
Mainly published to reduce greenhouse gases emissions, new building regulations, leads to a constant improvement of building components such as building envelopes and static insulation. Although, the effectiveness and the behaviour of the air-conditioning plants, validated by commissioning procedures, affect greatly the energy needs in buildings, through ventilation requirements. The main work of Annex 40 of the International Agency of the Energy reports on “Commissioning of Building HVAC systems for Improved Energy Performance”. The retro- and on-going commissioning of existing buildings HVAC systems can be achieved using many tools. In this annex, we focus on three which have several objectives and intervene in different phases of the commissioning process. One leads to the detection of faults whereas the others contribute to energy consumption evaluation. This paper presents a critical analysis of the various tools used and evaluates the potential of each tool in the commissioning phases under consideration, in order to determine the most convenient ones for the project in question. The work presented in this paper allows providing a helpful advice to the energy service company or to the technical and research institutes to determine the most adequate tool in terms of number of potential detected faults, precision in energy savings evaluation, and end-user’s assessment. A critical analysis is presented to evaluate three of these tools and apply them to a real building. It appears clearly that the PECI Guide, developed for new construction, is very useful in retro-commissioning procedures. Moreover, Emma-CTA and its new versions (CITE-AHU, etc.) represent excellent fault detection tools and diagnosis tools of AHU. For energy savings, the IMPVP tends to become an international standard in measurement and verifications procedures for the ESCO, in order to evaluate energy savings following retrofit. The main issue of our work is to evaluate the operability, potential, time consumed, and results of these tools when used by the HVAC operation staff.
This paper presents an investigation of the influence of surface radiation on indoor environmental parameters such as thermal comfort and indoor air quality. To achieve this objective, coupled heat ...transfer by mixed convection and radiation was numerically carried out inside a ventilated cavity. Air-CO2 mixture was considered as the working fluid. Uniform heat and CO2-concentration were applied at the bottom wall of the cavity. The boundary conditions of other walls were fixed at the external conditions. The same emissivity value was considered for all interior surfaces. An external fresh air enters at the cavity through an opening located on the top of the left vertical wall and exits from another one located at the bottom of the opposite wall. The mass, momentum, energy and chemical specie equations, coupled with the RNG k-ε turbulence model were solved via finite volume method. The obtained results indicate that the surface radiation presents slight effect on thermal comfort indexes, while the increasing of Rayleigh number enhances them. A good indoor air quality is insured inside the studied cavity.
► A method to determine thermal insulation and heat capacity for new buildings. ► Reflective – Newton method used to solve the problem, regarded as an inverse problem. ► Sensibility of the results to ...building's parameters numerically investigated.
Designing low-energy buildings has become a necessity, encouraged by thermal regulations, the need for energy savings and environmental awareness. Computer-aided thermal design of building walls is currently investigated using the latest optimization algorithms. This paper studies building multilayer walls by coupling a direct thermal model with a specific optimization algorithm. The direct problem solution is based on the Laplace transform of the quadrupole method, and then translated by numerical inversion into the time domain by the Fourier series method. The optimization model minimizes a least squares criterion between intended indoor temperatures and a direct response model. The work aims to optimize the thermal insulation and the heat capacity of wall layers and further building heating loads. An indoor temperature evolution is specified under fixed outdoor conditions in order to identify the composition of the building walls using an inverse resolution based on a reflective Newton algorithm applied to a direct quadrupole model.
The new building thermal regulations, mainly published to reduce greenhouse gases emissions, leads to a continuous improvement of building envelopes. On the other hand, the technical performance of ...the air-conditioning plants, ensured by commissioning procedures, becomes a key point for the control of energy needs in buildings. The essential work of Annex 40 of the International Agency of the Energy reports on “Commissioning of Building HVAC systems for Improved Energy Performance”. In this annex, the test of the IPMVP, International Performance Measurement and Verification Protocol, which is a significant and commonly used tool, is carried out among many others. This paper aims to present and detail the methodology of the IPMVP application and the results of four different calculation options applied to an existing building equipped with an innovative HVAC device, where outdoor airflow rate is controlled by indoor CO
2 rate. This work provides a helpful advice to the energy service company to determine the most adequate option in terms of accuracy, cost and speed of execution according to the available parameters (measurements, software) and the energy saving measure.
This article aims to present the coupling of a direct thermal calculation with an optimization algorithm to identify the thermal characteristics of a simplified building wall. The resolution of the ...direct thermal calculation is first based on an electric network representation that is numerically solved with a finite difference method. The optimization model minimizes a criterion, such as least squares, between the expected temperatures inside the building and the model response using a reflective Newton inverse iterative algorithm. The proposed optimization method is validated using an experimental study of a cubic wooden structure under controlled ambient conditions and a uniform heat source.
The effects of faults on an air handling unit (AHU) are often poorly evaluated (assuming indoor air quality (IAQ) problems), and under-estimated in consumption balances. Based on an experimental ...site, this paper presents a quantitative study of some different faults that can appear on AHUs.
Through a systemic analysis and a suitable modelling, the effects of several faults are simulated, using graphical software. Three families of faults are studied: control of a three-way valve, mixing box dampers (flow problems), and sensor inversion. Most of them find expression in an increase of the system consumption. The IAQ, seen here as the CO
2 rate, is studied thanks to the developed piece of software; the IAQ impact of faults is not accessible without such tool.
The software is then applied to a combination of several faults, in order to bring out major tendencies.
A perforated heat flux plate for building use is presented and compared with traditional full surface plates. Laboratory calibration tests using a guarded hot plate apparatus showed that the ...performance of the new perforated CAPTEC® plate is comparable to a solid, standard plate. However, in-situ tests with surface-mounted sensors in a building wall indicated that the CAPTEC® plates were reliable but their poor thermal contact and the edge effects in the perforations lead to an offset factor for the output voltage. The presence of perforations did not lead to any significantly improved measure due to evaporation or condensation on the wall. A basic simulation was performed to show the edge effects caused by the perforations and an experimental correction factor for the field measurements is proposed.
Energy performance and thermal comfort in historic and traditional urban environments are important because of the social and cultural requirement to conserve these areas as living entities, but also ...for the environmental obligation to decrease the impact of existing buildings globally. The objective of ENERPAT approach is to address this global challenge from the local perspective, through the co-creation of efficient solutions that improve the energy performance of historic areas considering local techniques and skills, taking into account the whole life cycle of the solutions, and supporting local economy and business. The objective is to test the efficiency and suitability of eco-renovation strategies that have been co-created with local stakeholders and are based on traditional energy conservation measures, as a way to work with locally-based business models that can safeguard cultural aspects and enable economic development. Two living labs have been established in the cities of Vitoria-Gasteiz (Spain) and Cahors (France) in two representative buildings of the historic urban area of each city. The living labs operate as inclusive multi-agent discussion arenas with a long-term vision, where multi-criteria co-creation processes are implemented to select conservation-friendly solutions based on local materials including criteria such as operational energy, impact on heritage values, quality of life, socio-economic development and easy logistics. The energy behaviour of the buildings and the hygrothermal performance of the external walls have been studied using on-site and laboratory experiments, through an efficient partnership between local authorities and universities. Likewise, local-based refurbishment solutions that were designed in the co-creation processes have been thermally characterised in the laboratory, through thermal conductivity and guarded hot box tests. Finally, the energy improvement of the whole renovation strategy has been simulated showing the enhancement of the two buildings.
•Energy efficiency of historic centres through eco-renovation and vernacular culture.•Energy transition based on co-creation and evolutionary development.•Urban labs to merge evidence-based knowledge with socio-economic considerations.•Architectural heritage is broadened to include traditional techniques.•Results of the co-creation process are tested with experimental and numerical work.
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