Emmanuel Essah

Computational fluid dynamics modelling of the air movement in an environmental test chamber with a respiring manikin

In recent years, computational fluid dynamics (CFD) has been widely used as a method of simulating airflow and addressing indoor environment problems. The complexity of airflows within the indoor environment would make experimental investigation difficult to undertake and also imposes significant challenges on turbulence modelling for flow prediction. This research examines through CFD visualization how air is distributed within a room. Measurements of air temperature and air velocity have been performed at a number of points in an environmental test chamber with a human occupant. To complement the experimental results, CFD simulations were carried out and the results enabled detailed analysis and visualization of spatial distribution of airflow patterns and the effect of different parameters to be predicted. The results demonstrate the complexity of modelling human exhalation within a ventilated enclosure and shed some light into how to achieve more realistic predictions of the airflow within an occupied enclosure.

Assessing stack ventilation strategies in the continental climate of Beijing using CFD simulations

ABSTRACT The performance of a stack-ventilated building compared with two other building designs have been predicted numerically for ventilation and thermal comfort effects in a typical climate of Beijing, China. The buildings were configured based on natural ventilation. Using actual building sizes, computational fluid dynamics (CFD) models were developed, simulated and analysed in Fluent, an ANSYS platform. This paper describes the general design consideration that has been incorporated, the ventilation strategies and the variation in meshing and boundary conditions. The predicted results show that the ventilation flow rates are important parameters to ensure fresh air supply. A predicted mean vote (PMV) model based on ISO-7730 (2005) and the predicted percentage dissatisfied (PPD) indices were simulated using custom field functions (CFF) in the fluent design interface for transition seasons of Beijing. The results showed that the values of PMV are not within the standard acceptable range defined by ISO-7730.

Domestic Cold Pitched Roofs in the UK - Effect of Using Different Roof Insulation Materials

Abstract The type and thickness of insulation on the topside horizontal of cold pitched roofs has a significant role in controlling air movement, energy conservation and moisture transfer reduction through the ceiling to the loft (roof void) space. To investigate its importance, a numerical model using a HAM software package on a Matlab platform with a Simulink simulation tool has been developed using insitu measurements of airflows from the dwelling space through the ceiling to the loft of three houses of different configurations and loft space. Considering typical UK roof underlay (i.e. bituminous felt and a vapour permeable underlay), insitu measurements of the 3 houses were tested using a calibrated passive sampling technique. Using the measured airflows, the effect of air movement on three types of roof insulation (i.e. fibreglass, cellulose and foam) was modelled to investigate associated energy losses and moisture transport. The thickness of the insulation materials were varied but the ceiling airtightness and eaves gap size were kept constant. These instances were considered in order to visualize the effects of the changing parameters. In addition, two different roof underlays of varying resistances were considered and compared to access the influence of the underlay, if any, on energy conservation. The comparison of these insulation materials in relation to the other parameters showed that the type of insulation material and thickness, contributes significantly to energy conservation and moisture transfer reduction through the roof and hence of the building as a whole.

Thermoeconomic Analysis and Evaluation of a Building-Integrated Photovoltaic (BIPV) System Based on Actual Operational Data

In this chapter, we considered a building-integrated photovoltaic (BIPV) system, which was installed at Yasar University in Izmir, Turkey, within the framework of an EU/FP7-funded project and has been successfully operated since February 8, 2016. The BIPV system consists of 48 crystalline silicon (c-Si) modules in 4 rows and 12 columns, and the total capacity is 7.44 kWp. We applied the specific exergy costing (SPECO) method to the BIPV system for the first time to the best of the authors’ knowledge. In this regard, we briefly introduced the BIPV system in this study first. We then used the SPECO method for assessing the performance of the BIPV system. Exergetic costs associated with the generated electricity varied between 0.21 and 0.36 €/kWhex for the selected days, with an average exergetic cost of 0.368 €/kWhex for the whole year.

Morphometric analysis of body and claw dimensions of building dwelling UK bat species: to aid knowledge of bat interactions with roosting surfaces

The increasing use of non-woven materials, such as breathable roofing membranes (BRMs) within buildings that either currently contain a bat roost or may do in the future, has led to concerns over bat safety by those involved in bat conservation in the UK. Whilst some information is currently available on the selection of roosts in roofs by bats, along with technical specifications of individual membranes, there is no research that has investigated the interactions between the two. Prior to determining the methods needed to test interactions between bats and BRMs, a series of preliminary investigations were conducted; including research and physical measurements on selected anatomical features of bats commonly found roosting in buildings in the UK. Data on body size and shape were gathered from a combination of experimental measurements of bat specimens (deceased) and information collated from literature. Data on bat claw morphology were collected by applying a method used to measure raptor talons, measurements obtained included; width, length and the curvature (hook ratio) of their claws. The results of this research provide additional information about bat body and claw morphometrics. It was found that bat species/group had a significant effect upon the length, width and curvature of the claws (to varying degrees). Pipistrelle species have the shortest and third narrowest claws, whereas serotines have the longest and widest claws on average. The curvature of the claws does not vary greatly between species; however, more variation was seen in the lower portion of the claws. The results from this research also demonstrate that the current standard industry tests do not represent the fine scale at which a bats claws interact with their roosting surfaces. Consequently, this information can be used to aid the development of industry tests for determining the suitability of BRMs for use in bat roosts.

Principles and Calibration of Solid Phase Microextraction Fibre (Passive Sampler) for Measurements of Airflow and Air Infiltration in Dwellings

Abstract Tracer gas techniques have been the most appropriate experimental method of determining airflows and ventilation rates in houses. However, current trends to reduce greenhouse gas effects have prompted the need for alternative techniques, such as passive sampling. In this research passive sampling techniques have been used to demonstrate the potential to fulfil these requirements by using solutions of volatile organic compounds (VOCs) and solid phase microextraction (SPME) fibres. These passive sampling techniques have been calibrated against tracer gas decay techniques and measurements from a standard orifice plate. Two constant sources of volatile organic compounds were diffused into two sections of a humidity chamber and sampled using SPME fibres. From a total of four SPME fibres (two in each section), reproducible results were obtained. Emission rates and air movement from one section to the other were predicted using developed algorithms. Comparison of the SPME fibre technique with that of the tracer gas technique and measurements from an orifice plate showed similar results with good precision and accuracy. With these fibres, infiltration rates can be measured over grab samples in a time weighted averaged period lasting from 10 minutes up to several days.