A Foundation Wall Heat Exchanger Model and Validation Study

Making use of foundation substructural elements as ground heat exchangers is an attractive option for larger non-residential buildings. An alternative to Energy Piles is to use wall substructures – so called diaphragm or screen walls – with embedded pipes that are partly below ground and partly exposed to basement spaces. This paper will describe the development of a model of such a heat exchanger that uses a weighting factor approach known as Dynamic Thermal Networks (DTN). This approach allows for detailed representation of the wall section geometry and multiple boundary conditions. In this case thermal boundary conditions are applied at surfaces representing the adjacent ground and the semiexposed basement wall surface in addition to the pipe surface. The weighting factors for the model have been derived using a parametric numerical model that has been developed using the OpenFOAM library. Validation of the model has been carried out using data from an extended series of thermal response test (TRT) measurements at a full-scale diaphragm wall heat exchanger in Barcelona. In this paper, development of the model using the DTN approach will be briefly described along with the parametric numerical modelling approach used to derive the weighting factor data. Validation test procedures will be presented along with comparisons between the predicted and measured fluid temperatures and heat transfer rates. Given some uncertainty in the experimental thermal properties, the model was able to predict the dynamics of thermal response over a range of operating conditions with reasonable accuracy and using very modest computational resources

Developing Analysis Approaches for Energy Walls

The use of diaphragm or bored pile walls as ground heat exchangers as well as embedded retaining structures has gained popularity in recent years. Dual use of structure foundations in this way has the potential to reduce the costs of associated ground source heat pump systems, hence providing opportunities for the take up of renewable heating and cooling in our cities. Such systems have been recently constructed as part of major infrastructure schemes in London and Paris. However, there are no standard analytical analysis approaches to permit routine design of the thermal aspects of these novel planar ground heat exchangers. Hence assessment of energy availability on most practical projects either (i) adapts existing methods from ground heat exchangers of different geometry, which runs the risk of incurring errors; or (ii) resorts to time consuming numerical simulation, often in partnership with a research organisation. Neither approach is sustainable for routine roll out of the technology beyond prestige projects. To start to fill this gap in knowledge, this paper presents the first feasibility assessment of developing specific analytical tools for use with energy walls

A Model of a Diaphragm Wall Ground Heat Exchanger

Ground thermal energy is a sustainable source that can substantially reduce our dependency on conventional fuels for heating and cooling of buildings. To exploit this source, foundation sub-structures with embedded heat exchanger pipes are employed. Diaphragm wall heat exchangers are one such form of ground heat exchangers, where part of the wall is exposed to the basement area of the building on one side, while the other side and the further depth of the wall face the surrounding ground. To assess the thermal performance of diaphragm wall heat exchangers, a model that takes the wall geometry and boundary conditions at the pipe, basement, and ground surfaces into account is required. This paper describes the development of such a model using a weighting factor approach, known as Dynamic Thermal Networks (DTN), that allows representation of the three-dimensional geometry, required boundary conditions, and heterogeneous material properties. The model is validated using data from an extended series of thermal response test measurements at two full-scale diaphragm wall heat exchanger installations in Barcelona, Spain. Validation studies are presented in terms of comparisons between the predicted and measured fluid temperatures and heat transfer rates. The model was found to predict the dynamics of thermal response over a range of operating conditions with good accuracy and using very modest computational resources

Effect of vitamin C and vitamin E on lung contusion: A randomized clinical trial study

ABSTRACT There is association between lung contusion (lC) and a progressive in fl ammatory response. The protective effect of vitamin C and vitamin E, as strong free radical scavengers on favourite outcome of (LC) in animal models,has been confirmed. Design: to evaluate the effect of vitamins, E and C on arterial blood gas (ABG) and ICU stay, in (LC), with injury severity score (ISS) 18 ± 2, due to blunt chest trauma. Methods: This study was a randomized, double-blind, placebo controlled clinical trial. Patients with (ISS)18 ± 2 blunt chest trauma, who meet criteria, participated in the study. A total of 80 patients from Feb 2015 to Jun2018and were randomly divided into 4 groups. Patients received intravenous vitamin E (1000IU mg), was (group I);intravenous vitamin C (500) (group II). Vitamin C + vitamin E = (group III), and intravenous distilled water = (control group) or (group IV). ABG, serum cortisol, and CRP levels were determined at baseline, 24 h and 48 h after the intervention. Results: a significant decrease in ICU stay in group III compared to other groups (p < 0.001). Co-administration of vitamin C and vitamin E showed significant increases pH (values to reference range from acidemia”), oxygen pressure, and oxygen saturation in group III compared to other groups (p <0.001). A significant decrease in carbon dioxide pressure was also detected after receiving vitamin C and vitamin E in group III, compared to other groups (p < 0.001). There was no significant difference cortisol and CRP levels between groups after the intervention. Conclusion: Co-administration of vitamin C and vitamin E, improve the ABG parameters and reduce I

Investigations into Thermal Resistance of Tunnel Lining Heat Exchangers

Geothermal energy is a promising and sustainable source that can reduce current dependence on conventional fuels for thermal energy production. To exploit this source of energy thermo-active geostructures such as tunnel lining heat exchangers are being investigated theoretically as well as experimentally. These geostructures are composed of concrete panels embedded with reinforcement cages fitted with absorber pipes. Several engineering projects in China, Finland and Italy have deployed such heat exchangers in tunnels. To achieve efficient energy production, characterisation of these systems require realistic models of the substructure heat exchanger. Therefore investigations into thermal resistance of the heat exchanger is vital. The present study is concerned with quantifying the thermal resistance of tunnel lining heat exchangers where the thermal boundary surfaces are applied at surfaces representing the adjacent ground and the exposed concrete, in addition to the pipe surface. Steady state temperature distribution in a two dimensional cross section of a tunnel lining heat exchanger is investigated using the boundary collocation least squares method. Design parameters including pipe and tunnel lining specifications are used as model inputs

Thermal energy transfer around buried pipe infrastructure

Decarbonisation of heating is essential to meet national and international greenhouse gas emissions targets. This will require adoption of a range of solutions including ground source heat pump and district heating technologies. A novel route to these solutions includes dual use of buried infrastructure for heat transfer and storage in addition to its primary function. Water supply and wastewater collection pipes may be well suited for thermal energy applications being present in all urban areas in networks already in proximity to heat users. However, greater understanding of their potential interactions with surrounding heat sources and sinks is required before full assessment of the energy potential of such buried pipe networks can be obtained. This paper presents an investigation into the thermal interactions associated with shallow, buried water filled pipes. Using the results of large scale experiments and numerical simulation it is shown that soil surface ambient conditions and adjacent pipes can both act as sources or sinks of heat. While conduction is the main mechanism of heat transfer in the soil directly surrounding any pipe, any adjacent water filled pipes may lead to convection becoming important locally. In the test case, the thermal sphere of influence of the water filled pipe was also shown to be large, at in excess of 4 m over a timescale of 4 months. Taken together, these points suggest that design and analysis approaches when using water supply and wastewater collection networks for heat exchange and storage need careful consideration of environmental interactions, heat losses and gains to adjacent pipes or other infrastructure, and in ground conditions for a number of pipe diameters from any buried pipe

IoT Expunge: Implementing Verifiable Retention of IoT Data

The growing deployment of Internet of Things (IoT) systems aims to ease the daily life of end-users by providing several value-added services. However, IoT systems may capture and store sensitive, personal data about individuals in the cloud, thereby jeopardizing user-privacy. Emerging legislation, such as California's CalOPPA and GDPR in Europe, support strong privacy laws to protect an individual's data in the cloud. One such law relates to strict enforcement of data retention policies. This paper proposes a framework, entitled IoT Expunge that allows sensor data providers to store the data in cloud platforms that will ensure enforcement of retention policies. Additionally, the cloud provider produces verifiable proofs of its adherence to the retention policies. Experimental results on a real-world smart building testbed show that IoT Expunge imposes minimal overheads to the user to verify the data against data retention policies.Comment: This paper has been accepted in 10th ACM Conference on Data and Application Security and Privacy (CODASPY), 202

Incomplete transcriptional dosage compensation of chicken and platypus sex chromosomes is balanced by post-transcriptional compensation

Heteromorphic sex chromosomes (XY or ZW) present problems of gene dosage imbalance between sexes and with autosomes. A need for dosage compensation has long been thought to be critical in vertebrates. However, this was questioned by findings of unequal mRNA abundance measurements in monotreme mammals and birds. Here, we demonstrate unbalanced mRNA levels of X genes in platypus males and females and a correlation with differential loading of histone modifications. We also observed unbalanced transcripts of Z genes in chicken. Surprisingly, however, we found that protein abundance ratios were 1:1 between the sexes in both species, indicating a post-transcriptional layer of dosage compensation. We conclude that sex chromosome output is maintained in chicken and platypus (and perhaps many other non therian vertebrates) via a combination of transcriptional and post-transcriptional control, consistent with a critical importance of sex chromosome dosage compensation

The Potential for Heat Recovery and Thermal Energy Storage in the UK Using Buried Infrastructure

Dispersed space heating alone accounts for 40% of UK energy use and 20% of CO2 emissions. Tackling heating and building cooling demands is therefore critical to achieve net zero ambitions in the UK. The most energy efficient way to decarbonise heating and cooling is through the use of ground source heat pumps and district heating technology. However, capital costs are often high, sometimes prohibitively so. To reduce investment costs, it is proposed to use buried infrastructure as sources and stores of thermal energy. Barriers to this innovative approach include lack of knowledge about the actual net amount of recoverable energy, and impacts on the primary function of any buried infrastructure, as well as the need for new investment and governance strategies integrated across the energy and infrastructure sectors. Additional opportunities from thermal utilisation in buried infrastructure include the potential mitigation of damaging biological and/or chemical processes that may occur. This paper presents a first assessment of the scale of the opportunity for thermal energy recovery and storage linked to new and existing buried infrastructure, along with strategic measures to help reduce barriers and start the UK on the journey to achieving of its infrastructure energy potential