In many industries and processes, heat exchangers are of vital importance as they are used to transfer heat from one fluid to another. These fluids can be corrosive to heat exchangers, which are usually made of metallic materials. This paper illustrates that corrosion is an important problem in the operation of heat exchangers in many environments, for which no straightforward answer exists. Corrosion failures of heat exchangers are common, and corrosion often involves high maintenance or repair costs. In this review, an overview is given of what is known on corrosion in heat exchangers. The different types of corrosion encountered in heat exchangers and the susceptible places in the devices are discussed first. This is combined with an overview of failure analyses for each type of corrosion. Next, the effect of heat transfer on corrosion and the influence of corrosion on the thermohydraulic performances are discussed. Finally, the prevention and control of corrosion is tackled. Prevention goes from general design considerations and operation guidelines to the use of cathodic and anodic protection.

No abstract

No abstract

In this work, a proof of concept design for a poultry meat farm is studied. The design aims to be climate-neutral and energy-flexible by applying different technologies such as PV panels, PVT panels, BEO field, and high and low-temperature heat pumps. In order to size these systems, the farm's required heating, cooling power and (de)humidification rate has to be estimated, which is the focus of the current paper. For this purpose, a model was created in the Python environment. Based on the building's current design, expected weather conditions throughout a model year, and the required conditions for the chickens' well-being, the heating and cooling loads are calculated. The analysis does not yet take into account which technology is used to supply the heat as the sizing will be done based on the results of this analysis. In addition to the 'standard' climate requirements, some pens will be used to study the behaviour of the chickens during alterations in the temperature and humidity of the pen. These tests are predefined and the HVAC installation should be able to handle these test conditions as well. The results of the model can be used as a guideline to size the different HVAC systems. However, as the model is based on assumptions and simplifications, a sensitivity analysis was performed as well. This analysis shows that the conductive losses are small compared to ventilation and infiltration losses. The air changes per hour of the farm have a great impact on the total required heating and cooling power. Therefore, attention should be given to the air-tightness of the chicken pens to reduce the required installation size.

No abstract

In this study, the performance of ventilation systems with heat recovery in residential buildings with a low energy demand for heating was evaluated. In a completely heated building, the percentage of useful recovered heat will be equal to the nominal effectiveness of the heat exchanger. In the case some rooms are not heated, they will still receive preheated air. This part of the recovered heat will not directly increase comfort, so it does not completely contribute to the energy savings of the building. Simulations were done with TRNSYS to assess the percentage of usefully recovered heat. This value was found to be lower than the nominal effectiveness, but varying with several parameters.

Agriculture and intensive farming are a large source of green house gas emissions. Since currently about 70% of its energy is coming from polluting fossil fuels, it is necessary to implement renewable technologies in stables, which is currently being investigated with the RES4LIVE project. Some of the possibilities are: photovoltaic and thermal solar panels, heat pumps, ventilation energy recovery, wind energy and manure energy recovery. To evaluate the extent to which these technologies can be used and combined, and to estimate the performance and cost, a thermal model is being developed. This numerical model (although not CFD) is currently focused on pig stables and takes different heat losses (through ventilation and through the building envelope) and heat gains (heating systems and heat generation by the animals) into account. The results are still preliminary, but the goal is to accurately determine the heating and cooling load of each zone in the stable. This will eventually allow to make a selection and sizing of the proper renewable technologies.

According to the official statistical reports, gas-fired boiler units still remain to be one of the main equipment types for meeting the space heating and daily hot water demand of the residential dwellings across the European Union. Due to the prevalence of the natural gas grid and performance stability, gas-fired boilers are considered to remain as one of the standard energy sources. On the other hand, even though gas-fired water heating technology is a well-known concept, existing numerical models found in the literature are often case-specific with poor reusability mostly reflected in fitted efficiencies. Algorithms behind these models usually require the input of large amount of hardly attainable design characteristics of the units. In this paper, a modelling method for acquiring the performance of a heating gas-fired condensing boiler unit will be shown. The model is based on the limited input data available in the official characteristics of the units issued by the relevant manufacturers. The simulations are programmed by using the programming language Modelica and the software tool Dymola. The model is based on the fixed natural gas intake which combusts into a stable mixture of the combustion gases that further heat the circulating water. During the heat transfer process inside the condensing boilers there is a possibility for condensate formation out of the water vapour of the combustion gases which increases the efficiency of the unit. The formation of condensate, however, is depending on the return water temperature of the unit which has to be lower than the dew point temperature of the combustion gasses. The goal of this research is to determine how accurate can performance indicators of gas-fired boilers be attained with the use of a limited amount of available input data together with clearly defined assumptions that follow the modelling methodology.