Performance and control of domestic ground-source heat pumps in retrofit installations

Heat pumps are an essential technology for decarbonisation of domestic heating in the UK. This paper reports on the performance in use of a group of ground-source heat pumps, and in common with other UK studies finds that the seasonal performance is not as good as that reported in trials from continental Europe and that the system controls are unsatisfactory. Control improvements are investigated via a model of the dwelling and heat pump as a combined system, from which the thermal time constant of the building is identified as a critical factor that needs to be considered in retrofit projects incorporating heat pumps. The validity of the conventional practice (and advice from installers to users) of allowing heat pumps to run continuously is tested and bounded. Techniques for improving control are outlined and reasons for the poorer performance in the UK examined with the conclusion that heat pumps need to be better matched in capacity and control to the size and thermal characteristics of UK dwellings. Implementation of these findings by heat pump manufacturers and installers could promote a more rapid transition to renewable heat both in the UK and internationally wherever similar housing stocks and climates exist.     

Farm building design and animal heat losses

Studying heat emission from livestock is not a common feature of building research work. Yet knowledge of animal heat losses is as important to designing farm buildings as knowledge of human thermal response is to the design of buildings for people. This thermotechnical work has become highly specialised in Denmark, leading to published heat losses for cattle, pigs and poultry, explained here by a research engineer at the Danish Building Research Institute's Farm Buildings Section.     

Residential heat pump installations: the role of vocational education and training

Meeting European emissions targets is reliant on innovative renewable technologies, particularly ‘renewable heat’ from heat pumps. Heat pump performance is driven by Carnot efficiency and optimum performance requires the lowest possible space heating flow temperatures leading to greater sensitivity to poor design, installation and operation. Does sufficient training and installer capacity exist for this technology? This paper situates the results of heat pump field trial performance in a socio-technical context, identifying how far installer competence requirements are met within the current vocational education and training (VET) system and considers possible futures. Few UK installers have formal heat pump qualifications at National Vocational Qualification (NVQ) level 3 and heat pump VET is generally through short-course provision where the structure of training is largely unregulated with no strict adherence to a common syllabus or a detailed training centre specification. Prerequisites for short-course trainees, specifically the demand for heating system knowledge based on metric design criteria, is limited and proof of ‘experience’ is an accepted alternative to formal educational qualifications. The lack of broader educational content and deficiencies in engineering knowledge will have profound negative impacts on both the performance and market acceptance of heat pumps. Possible futures to address this problem are identified.     

Measured heat losses through a real ground floor slab

The measured variation of heat losses across the floor slab emphasize the potential benefits to be gained from the use of edge insulation. In general, thermal transmittance values calculated from the measured data are found to be in reasonable agreement with values determined from design guides.     

沼气热泵工质热力参数算法及软件设计研究

研究了制冷工质热力参数算法并应用线性插值的数学方法设计了制冷工质热力参数计算查询软件,该软件功能强大可以查询多种制冷工质的热力参数,另外还具有操作简单,使用方便等优点,可解决在制冷工程计算时查表不方便并且许多参数不能查到的问题,减少了工程的计算量,为工程计算人员提供了许多便利。     

Theoretical calculations of the steady-state heat losses through a slab-on- ground floor

A new analytical expression for the two-dimensional steady-state heat loss from a slab-on-ground floor is derived as a function of the floor width, wall thickness, ground conductivity, and surface film conductance. Two approximate forms, which are easier to calculate, arealso given. Analogous approximate expressions are obtained for the three-dimensional case. Comparisons with previous theoretical work generally show good agreement, except for very small floors, for which the expressions derived here predict somewhat lower heat losses.     

Double skin façade's effects on heat losses of office buildings in Istanbul

As is known double skin façade applications have an important role on passive solar strategies. In this paper, heat losses of a single skin and a double skin façade office buildings were compared to show the effect of double skin on building energy demand for winter period in Istanbul. Calculations have been carried out for the January, which is assumed as the representative month of winter period in Istanbul considering Istanbul's climatic conditions. However there is no any double skin façade application in Istanbul, the thermal effect of the double skin has been theoretically analysed to show the effect of double skin façade on heat losses if this technology would be applied by the construction industry in Turkey. In this study a new method is used in double skin façade's heat losses calculations. The realization of the proposed method is composed of two main steps. The first step is formed from the modification of a previous method, which is proposed by Todorovic, to calculate inter-space temperature. For the second step inter-space temperatures calculated in the first step have been accepted as outdoor air temperature and time dependent heat transfer through the inner skin of the envelope has been calculated by using finite difference numerical approach. It has been assumed that the space between two skins is closed since the calculations have been made for the winter period. It has been concluded that heating energy consumption is significantly reduced in double skin façade building for winter conditions in Istanbul.     

Determination of the convective heat transfer coefficient in three-dimensional inverse heat conduction problems

A thin steel plate probe (24 mm wide×24 mm long×3 mm thick) surrounded by insulation except for the exposed surface was constructed. Using the temperature measurements of the steel plate and the heat flux measured by a Gardon gauge and with the assistance of numerical calculations, two methods based on three-dimensional inverse conduction problems are developed to determine the convective heat transfer coefficient in fire experiments. The first one is based on optimisation of the predictions of the temperature of the steel plate using different heat transfer coefficients, while the second adopts a “predictor–corrector” method to determine the instantaneous heat transfer coefficient. Validation of both methods is accomplished by performing experiments in the cone calorimeter at a known constant heat flux. Subsequently, the two methods are applied to experiments in enclosures to examine the sensitivities of the two methods.     

Hydraulic performance of sprinkler installations

Some sprinkler system designers place total reliance upon rules and pipe schedules, while others take an opposing view by insisting that every system should be calculated. The authors suggest a middle ground approach that offers economic advantages, but does not significantly alter system performance. Mather & Platt, Ltd. Note: This paper was presented at the 71st Annual Meeting of the National Fire Protection Association on May 16, 1967 in Boston, Massachusetts.     

Natural ventilation of indoor spaces while minimizing heat losses: Theoretical and experimental investigation

Limiting heat losses during ventilation of indoor building spaces has become a basic aim for architects, particularly since the oil crisis of 1970. Much experience has been gained in terms of ventilation of indoor spaces. Nevertheless, due to the complex applications, attempts to create a theoretical base for solving the problems related to the issue are limited, especially determining the minimum ventilation period required within a designated space. In this paper we have approached this matter, both theoretically and experimentally. The conclusion we reached was that controlled ventilation of spaces through vent holes that successively open and close at regular time intervals can limit the excessive circulation of air masses, which in turn limits heat losses.     

Steady-state heat losses from a building floor slab with vertical edge insulation—I

The steady-state heat loss from an infinitely long slab-on-ground floor, insulated at its edges by vertical insulation into the ground, is calculated in two dimensions from a Fourier series solution of the temperature field in the ground. The temperature at the surface of the ground is assumed to change linearly from the inside of the building to the outside over a distance representing the wall thickness. The heat loss is calculated as a function of d/L, where d is the insulation depth and L is the building half-width. As d/L increases, there is a fairly rapid decrease in the heat loss at small values of d/L, and a much slower decrease beyond d/L = 1. The results indicate that it would be necessary to install an impracticably large depth of insulation to achieve a reduction in the floor heat loss comparable to that obtainable by insulating a wall.     

Determination of orifice diameter for horizontal pipelines in layers for composing windrows via variation of pressure losses

Compressed air plays an important role in forced aeration composting systems; the lateral outlet orifices on the main pipeline must be properly sized to maintain a pressure drop of less than 5% at the output of each orifice. Organic matter (OM) was aerated at a rate of 0.557 m³ air·d^-1·kg^-1, as determined by dry weight (DW), and the internal temperature and humidity of the windrows were monitored. The calculated variation of the pressure loss for the pipelines in the experimental windrow was between 1.53% and 2.56% at a maximum internal temperature of 70.8°C, unlike the conventional windrow, which reached a maximum temperature of 47.1°C. In both systems, the humidity was greater than 50%. The cost per metre for commercial scale implementation is equivalent to US$21.22, considering the use of alternative materials with the necessary mechanical and thermal resistance values.     

The effect of regenerative losses on the efficiency of a Stirling heat engine at maximum power output

A more realistic cycle model is established for discussing the performance of the Stirling heat engine with regenerative losses. The power output is adopted as an objective function for optimisation. The maximum power output and the corresponding efficiency of the Stirling heat engine are derived. The effect of regenerative losses on the efficiency at maximum power output is expounded. The times of four processes in the Stirling cycle are allotted optimally. Some new conclusions are obtained.     

Determination of specific heat capacity by transient plane source

A standard TPS measurement gives the thermal conductivity and thermal diffusivity of an isotropic material which in turn gives the heat capacity. The thermal properties of an anisotropic material can be measured if the heat capacity is known. A method for heat capacity measurement exists, where the TPS sensor is attached to a sample container which is surrounded by insulation. However, it's based on an assumption of negligible heat losses which leads to uncertainties in the results. From that position, this work aims to model the heat losses from the specific heat measurements with TPS. A new set-up is introduced, where the sensor with the container hangs freely in a steel tube to get more predictable heat losses. The results show that the measurements can be modelled as a network of lumps connected by conductances approximated as constant. Thereby, the conductances out from the system can be solved from a reference measurement and used as input for a model of a measurement with a sample. The model seems to underestimate the heat capacity, which might be a consequence of temperature dependent effects on the conductances from convection. The tube in the set-up could be evacuated to minimize those losses.     

Clay solutions in the construction of foundations and underground installations

Soil Mechanics and Foundation Engineering -