Differences in perception of indoor environment between Japanese and non-Japanese workers

Field surveys were conducted at an office with multinational workers in Japan to investigate the differences in the way groups of occupants perceive the environment under real working conditions. Returned questionnaires, 406 in total, were classified into three groups according to their nationality and sex. Only 26% of workers reported their working environment to be comfortable. A significant neutral temperature difference of 3.1 °C was observed between the Japanese female group and the non-Japanese male group under their usual working conditions. Japanese females reported a higher frequency of sick building syndrome related symptoms compared to other groups. Occupant comfort and reported frequency of SBS symptoms were closely related to deviation of the thermal sensation vote from neutral. The thermal environment was found to be a major factor affecting occupant comfort in the concerned office. Differences in the perception of the indoor environment were negatively affecting the ratings of their working environment.     

A comparative analysis of short-term and long-term thermal comfort surveys in Iran

This paper describes two field studies of thermal comfort conducted in Ilam, a city located in western Iran. The first study consisted of two short-term surveys carried out during two climatically extreme periods—a hot summer and a cold winter—in 1998. The second study consisted of a long-term survey that collected data throughout the whole of 1999. Both studies were performed in naturally ventilated buildings. This paper shows some comparative analysis between the findings from the short-and long-term studies. For the hot season the neutral temperatures from the short-and long-term studies were 28.4 and 26.7 °C, respectively. For the cold season the short-and long-term neutral temperatures were 20.8 and 21.2 °C, respectively. The results show a very good agreement between both studies in Iran. The main points of interest from the studies were the variability of acceptable conditions, a good relationship between neutral temperature and room temperatures and also, more importantly, between indoor comfort and outdoor conditions. The findings reveal that the people in the study could achieve comfort at higher indoor air temperatures compared with the recommendations of international standards such as ISO 7730.     

Phenomenological model of binary-series viscosity for analysing rheological properties of a paraffin using validated experiments

This paper presents a theoretical and experimental study on the rheological behaviours of a grade of paraffin that is intended for use in environmental control systems for the purpose of thermal storage. This research concentrates on the paraffin flow properties in a laminar flow. In the experiments, when the paraffin temperature is greater than 291.15 K, the rheological behaviours of the paraffin obey the power-law principles. However, as the paraffin temperature reduces to 291.15 K or lower, the behaviour index tends to decrease with the shear rate, and thus, the rheological behaviours of the paraffin cannot be defined by the power-law model effectively. In the non-power-law phase, the solid properties of the material become increasingly apparent as the temperature gradually reduces. Simultaneously, the paraffin fluidity decreases. Therefore, a new phenomenological model of binary-series viscosity is proposed. The binary model provides an effective definition of the rheological properties of the paraffin in the non-power-law phase (the corresponding material temperatures range from 291.15 K to 288.15 K). In general, the paraffin-specific pressure drop in a horizontal pipe is approximately 1.4–6.0 times that of water at the same temperatures.     

Numerical procedure for predicting annual energy consumption of the under-floor air distribution system

As compared with the mixing system, indoor air temperature stratification in the under-floor air distribution (UFAD) system offers an opportunity for cooling load reduction in the occupied zone. This stratification is a major feature that offers the energy saving potential, but it has not been thoroughly taken into account in most energy simulation programs. In this article, a numerical procedure, based on coupling two types of modeling, i.e., CFD (computational fluid dynamic) simulation and dynamic cooling load simulation, is proposed to predict annual energy consumption. The dimensionless temperature coefficient is first defined in the UFAD system and obtained from CFD simulation, based on the boundary conditions from a cooling load program ACCURACY. According to this coefficient, temperature stratification input to ACCURACY is then revised to calculate the updated supply and exhaust air temperatures for final annual energy prediction. To demonstrate the method, a small office room is investigated using Hong Kong weather data. With the constant air volume (CAV) supply in the UFAD system, it is found that the dimensionless temperature coefficient is almost a constant, when the locations of heat sources are fixed. As compared with the mixing system, the UFAD system derives its energy saving potential from the following three factors: an extended free cooling time, a reduced ventilation load, and increased coefficients of performance (COP) for chillers.     

Design and optimization of hybrid solar-hydrogen generation system using TRNSYS

Solar thermal systems are an efficient utilization of solar energy for hot water and space heating at domestic level. A Solar Water Heater (SWH) incorporating an Evacuated Glass Tube Collector (EGTC) is simulated using TRNSYS software. Efficiency parameters are pointed, and a parametric optimization method is adopted to design the system with maximum conceivable efficiency. In the first part, the selection of refrigerant for heat transportation in SWH loop is presented. A set of 15 working fluids are chosen, and their chemical properties are computed using NIST standard software (REFPROP). The selected working fluids are tested in the system under study and plots for energy gain and temperature are plotted using TRNSYS. Results showed that ammonia (NH₃) having specific heat 4.6kJ/kg-K and fluid thermal conductivity 2.12 kJ/hr-m supplies peak energy gain of 7500 kJ/h in winter and 8900 kJ/h in summer season along 120 °C temperature rise. On the other hand, R-123 having specific heat 0.65kJ/kg-K and fluid thermal conductivity 0.0293kJ/hr-m showed inferior performance during the simulation. A solar-hydrogen co-generation system is also designed and simulated under low solar insolation and warm climate regions to study annual hydrogen produced by the hybrid system. System comprises main components: a PV array, an electrolyzer, a fuel cell, a battery, a hydrogen storage unit and a controller in the complete loop. Results of Hydrogen cogeneration system provide 7.8% efficiency in the cold climate of Fargo North Dakota state due to lower solar insolation. While hot climate condition of Lahore weather provides efficiency of 11.8% which satisfy the statistics found in literature.     

Prediction and optimization of the performance of parabolic solar dish concentrator with sphere receiver using analytical function

Parabolic solar dish concentrator with sphere receiver is less studied. We present an analytic function to calculate the intercept factor of the system with real sun brightness distribution and Gaussian distribution, the results indicate that the intercept factor is related to the rim angle of reflector and the ratio of receiver angle to the optical error when the optical error is larger than or equal to 5 mrad, but is related to the rim angle, receiver angle and optical error in less than 5 mrad optical error. Furthermore we propose a quick process to optimize the system to provide the maximum solar energy to net heat efficiency for different optical error under typical condition. The results indicate that the parabolic solar dish concentrator with sphere receiver has rather high solar energy to net heat efficiency which is 20% more than solar trough and tower system including higher cosine factor and lower heat loss of the receiver.     

Jet impingement heat transfer in a frost-free refrigerator: The influence of confinement

Heat transfer characteristics of a slot air jet (width w) impinging on a circular cylinder (diameter d = w) located 5d from the jet exit in a confined space have been studied for Reynolds number (based on cylinder diameter and mean jet velocity) in the range of 1000–12,000. This situation is found in a frost-free refrigerator, amongst other rapid food refrigeration applications. The results reveal that the slot jet impinging on a circular cylinder in a confined space yields heat transfer rates that are between those for the corresponding uniform cross-flow (lower limit) and slot jet impingement on a non-confined cylinder (upper limit) cases. A dimensionless confinement spacing H/d = 10 was found at which the heat transfer rate was a minimum. CFD analysis revealed that this was due to periodic jet flapping and generation of large flow structures between the cylinder and the confining wall.     

Low-carbon measures for Fiji's land transport energy system

Road transport in Fiji is fully dependent on petroleum fuels. This study is a first for Fiji where fuel demand for land transport is studied under some clean transportation strategies. Long-range Energy Alternatives Planning (LEAP) tool is used with 2016 as the base year and 2040 as the end year. In 2016, approximately 337 million litres of fuel was used with an associated GHG emission of around 864 Gg of CO_2e, which increases to 1158.4 Gg by 2040 in Business as usual (BAU) scenario. Several measures are explored to reduce the fuel consumption in the land transport sector in Fiji.     

On the heating potential of buried pipes techniques — application in Ireland

The heating potential of a single earth-to-air heat exchanger as well as of a multiple parallel earth tubes system has been investigated in this paper using real climatic data. The heating system consists of a single tube or multiple parallel tubes, buried in the ground, through which ambient air is propelled and heated by the bulk temperature of the natural ground. The dynamic thermal performance of the system during the winter period and its operational limits have been calculated in Ireland using an accurate numerical model. For this reason multi-year ambient air and soil climatic measurements for the city of Dublin have been used as inputs to the model. Furthermore, an extensive sensitivity investigation was carried out in order to evaluate the effect of the main design parameters on the system's heating capacity. The key variables influencing the performance of earth-to-air heat exchangers were considered to be pipe length, pipe radius, air velocity inside the tube and pipe depth below the surface of the earth. Cumulative frequency distributions of the air temperature at the pipe's exit have been developed as a function of all the input parameters.