Heat Source Selection Research Articles

Investigation on the thermal performance and economy of a solar assisted air source heat pump domestic hot water system

In order to increase the utilization of renewable energy and reduce carbon dioxide emissions, a solar assisted - air source heat pump (SA-ASHP) domestic hot water supply system is proposed, designed and built, the thermal performance and economy are numerically simulated and experimentally verified, the optimal design parameters are determined based on the economic optimization analysis. The results show that the coefficient of performance (COP) of air source heat pump (ASHP) varies from 2.62 to 3.93 and the COP of SA-ASHP system varies from 2.76 to 6.26. The solar fraction varies from 8.83% to 45.51%, and varies greatly in different seasons. The simulated heat collection of solar collector, the power consumption and heating capacity of ASHP, and the total power consumption of water pump are in good agreement with the measured results. Compared with the existing SA-ASHP system, the annual cost has decreased by 1998.32USD, annual cost converted from initial investment has decreased by 629.08USD, operating cost has decreased by 1369.25USD and total power consumption has decreased by 16897.79 kWh of the optimized SA-ASHP system. The optimum ratio between the input power of ASHP and the collector area is 0.078 kW/m2. The research results play an important role in guiding the design, operation and heat source selection of domestic hot water (DHW) system in student dormitory.

A Review of Numerical Simulation of Laser-Arc Hybrid Welding.

Laser-arc hybrid welding (LAHW) is known to achieve more stable processes, better mechanical properties, and greater adaptability through the synergy of a laser and an arc. Numerical simulations play a crucial role in deepening our understanding of this interaction mechanism. In this paper, we review the current work on numerical simulations of LAHW, including heat source selection laws, temperature field, flow field, and stress field results. We also discuss the influence of laser-arc interaction on weld defects and mechanical properties and provide suggestions for the development of numerical simulations of LAHW.

An Approach for Efficient Heat Source Selection in Long-Term Expansion Planning of Urban District Heating Systems

This study proposes an approach to selecting efficient heat sources in the context of long-term expansion planning for urban district heating systems. The approach includes two stages: synthesis and optimization. During the synthesis stage, potential heat source structures are generated using graph grammars. In the optimization stage, the most effective combination of heat source equipment is selected based on minimum construction costs, heat network costs, and pollutant emissions fees. Iterative linking of these two stages provides a coherent solution for determining the structure and parameters of heat sources, for streamlining the process of performing computational studies. The proposed approach is a comprehensive and cost-effective method for selecting heat source structures for urban district heating systems.

Technical, Energetic and Economic Optimization Analysis of Selection of Heat Source for Municipal Sewage Sludge Dryer

The treatment of growing production of municipal sewage sludge has become a significant global problem. Drying of digested sewage sludge is a promising alternative to sludge disposal at dumping sites. The research objective of this study was to find the optimal heat source for a sludge drying plant in a large municipal sewage treatment plant (people equivalent: 250,000). Two boundary heat supply cases were analyzed in the paper: cogeneration of heat and power (CHP) units, internal combustion (IC) engines fired with natural gas, and plant supplied with a gas boiler. The aim of the research was to find the optimal size of the cogeneration unit cooperating with the gas boiler as heat sources for a given drying plant case with the maximum net present (NPV) value as the objective function. The results of the conducted optimization show higher profitability of cases with larger cogeneration unit. For the basic assumptions, the maximum NPV is obtained for the largest analyzed CHP unit: 1300 kW of thermal power output. Sensitivity analyses show that the varying gas and electricity prices can relocate the NPV maximum towards smaller CHP sizes. A supplementary energy analysis shows that implementing larger CHP units yields a higher energy efficiency of the system, up to 0.52.

Life in the suburbs: artificial heat source selection for nocturnal thermoregulation in a diurnally active tropical lizard

Abstract. The rapid expansion of urban environments invariably presents a novel series of pressures on wildlife due to changes in external environmental factors. In reptiles, any such changes in temperature are critical since thermoregulation is the key driver in the function of many physiological processes. How reptiles adapt to such changes may vary from those species that are impacted negatively to others that have the behavioural flexibility to exploit new conditions. In this paper we describe retreat site selection, movements and aspects of the thermal ecology of the African lizard Agama agama in urban environments of West Africa. In early evening lizards began movement from late-afternoon core activity areas and ascended the walls of houses for overnight retreats. A high proportion retreated to locations in groups under or on top of warm electrical panels. The thermal potential these panels offered was the attainment of body temperatures equal to or higher than the minimum preferred body temperature (PBT ≈ 36 ∘C in A. agama) and hence increased physiological performance. The lizards that took advantage of the heat sources travelled further each day to and from diurnal activity areas than individuals that spent the night high on walls but not next to heat panels. There were both potential costs (enhanced predation pressures) and benefits (impacts on thermal ecology, retreat site selection) of this behaviour for lizards living in urban environments.

Analysis of heat source selection for residential buildings in rural areas

The research aiming to check whether the output of currently installed boilers matches the use requirements together with estimation of their energy efficiency was carried out on a group of 84 single-family residential buildings located in rural areas. Heating and hot water energy needs were calculated for each building in order to determine the use requirements. This enabled verification whether the currently installed boilers match the actual use requirements in the buildings. Based on the calculations it was determined that the designed average boiler output in the group of buildings subject to analysis is 15.7 kW, whereas the mean rated output capacity of boilers installed therein is 25.4 kW. On average, the output capacity of the installed boilers exceeds the use requirements for the buildings by 60%. To calculate the energy efficiency of boilers, the mean annual boiler output capacity use coefficient was determined. For boilers selected on the basis of standard calculations, the mean coefficient is 0.47. For boilers currently in use it is 0.31, less than the above figure. The above calculations show that if boilers were correctly selected in compliance to the building needs, then the average estimated seasonal efficiency of 65% would be feasible. However, in the current state the achievable efficiency is approx. 55%.

A comprehensive design methodology of organic Rankine cycles for the waste heat recovery of automotive heavy-duty diesel engines

One of the most promising approaches to recover the waste heat from internal combustion engines is the Organic Rankine Cycle owing to its efficiency and reliability. The design optimization of ORC, however, is nontrivial because there exist many design variables and practical considerations. The present paper proposes a comprehensive design methodology to optimize the Organic Rankine Cycles (ORC) considering a wide range of design variables as well as practical aspects such as component limitations and costs. The design process is comprised of three steps: heat source selection, candidate fluid selection, and thermodynamic cycle optimization. In order to select the best waste heat source, the available energy and other practical considerations of various heat sources have been compared. Among others, the Exhaust Gas Recirculation (EGR) cooler is found to be the best heat source, and thus used for the rest of this study. Based on a systematic working fluid analysis, Ethanol, Pentane, and R245fa are selected as three candidate fluids. For the comprehensive ORC optimization, four types of cycle layouts are considered; 1) subcritical cycle without a recuperator, 2) subcritical cycle with a recuperator, 3) supercritical without a recuperator, and 4) supercritical cycle with a recuperator. Four cycle layouts coupled with three candidate fluids give a total of twelve cycle analyses. Results show that the best performance is provided by the regenerative subcritical cycle with Ethanol, while the solution with minimum capital cost is the subcritical cycles with Ethanol but without a recuperator.

The ecological and economic aspects of a low emission limitation: a case study for Poland

The purpose of this study is to demonstrate ecological benefits of the thermal modernization of the central heating system in terms of the replacement of the central heating boiler for a modern boiler that is characterized by economically and ecologically beneficial parameters of the operation. It is particularly important in industrial regions where the concentration of harmful gases is high. An example is a region in Poland, which is the most industrialized and urbanized. The methodology is underpinned by life cycle thinking. The evaluation of the environmental benefits resulting from the modernization of heat sources was made with the use of life cycle assessment (LCA) technique, which was conducted according to the methodology defined in standards ISO 14040 and ISO 14044, using assessment methods included in Sima Pro 7 program with reference to a so-called representative building. The calculations were based on the assessment procedure of Ecoindicator 99, which allows for the presentation of the impact results with respect to 11 impact categories and/or three damage categories. The LCA analysis of the considered heat sources points out unambiguously the most environmentally friendly option with a gas boiler combined with a solar collector. Nevertheless, this option belongs to one of the most expensive solutions of supplying thermal energy in the house. The optimum appears to be a variant using the ecological fuel for biomass, due to widely available biomass in the whole country, a low impact on the environment, the lowest operating costs and moderately high investment costs. The replacement of a low-efficient heat source in the municipal economy is the most energetically effective undertaking. It should be emphasized that the replacement of the inefficient boiler provides the greatest ecological effect in relation to investment costs. The aspect of the heat source selection is not only justified by economic and ecological reasons; it primarily results from the local availability of fuel. The use of the environmental technique—the assessment of the product life cycle—to support the decision of the heat source selection becomes a significant aspect in helping investors make environmentally friendly choices.

Optimal Hierarchical Decision-Making for Heat Source Selection of District Heating Systems

With the rapid development of China’s urbanization, the proportion between the heating consumption and the energy consumption of the whole society keeps rising in recent years. For a district heating system, the selection of the heat source makes significant impact on the energy efficiency and the pollutant emissions. By integrating the methods of the Analytic Hierarchy Process (AHP) and the Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE), a multiple-attribute decision-making scheme for the heat source selection of district heating systems is proposed in this paper. As a core part of this scheme, a comprehensive benefit index with hierarchical parallel structure is constructed. The economic benefit, environment benefit, and technical benefit can be reflected with a certain percentage in the comprehensive benefit index. To test the efficiency of the proposed scheme, a case study for a large-scale district heating system in Beijing is carried out, where five kinds of heat sources (water source heat pump, ground source heat pump, gas-fired boiler, coal-fired boiler, and oil-fired boiler) are taken into account. The analysis and instructions for the final sorting result are also demonstrated.

Ultraviolet light and heat source selection in captive spiny-tailed iguanas (Oplurus cuvieri)

Three experimental manipulations were conducted to assess the influence of heat source selection and active thermoregulation on ultraviolet (UV) light exposure in captive spiny-tailed iguanas (Oplurus cuvieri) at the Jersey Wildlife Preservation Trust. Four replicates per manipulation were conducted on six individual lizards. All animals were tested in a separate enclosure to which they were acclimated before observations. Data on choice of thermal sources were collected during the first 2 hr of light, when lizards were actively thermoregulating. Animals were allowed to choose between incandescent light, UV light and a non-light heat source (thermotube) in different combinations. Recorded temperatures close to the incandescent light (37°C) were always significantly higher than at the thermotube (33°C) and at the UV light (29°C). Manipulation 1 offered the animals a choice of an UV light and an incandescent light as thermal sources. Manipulation 2 presented animals with the thermal choices in Manipulation 1, but substrates under each source in Manipulation 1 were switched. In Manipulation 3, animals could choose between an incandescent light and the thermotube. All studied lizards were significantly more attracted to the incandescent light than to the UV light or thermotube. Incandescent light elicited a significantly higher proportion of basking behaviors in all individuals than the other sources. A high proportion of time basking was also spent in front of the thermotube but fewer individuals and less time were spent basking under the UV light. Heat source selection was generally found to be independent of substrate. Management applications of this preference are suggested for juvenile diurnal heliothermic iguanids. Zoo Biol 16:391–401, 1997. © 1997 Wiley-Liss, Inc.

Mission Design Drivers for Closed Brayton Cycle Space Power Conversion Configuration

Future space power requirements will vary from the subkilowatt range for deep space probes, to the hundreds of kilowatts range for a lunar base, to the multimegawatt range for interplanetary propulsion systems. Closed Brayton cycle (CBC) power conversion has the flexibility to be used in all these power ranges and with a variety of heat source options such as isotope, solar, and nuclear. Each of these types of heat sources has different characteristics that make it more appropriate for particular mission profiles and power output ranges. Heat source characteristics can also be major design drivers in the closed Brayton cycle design optimization process. This paper explores heat source selection and the resulting CBC system designs, and discusses optimization methods as a function of the main design drivers. Such power system requirements as power level, man-rated radiation shielding, fuel costs, eclipse/darkness duration, system mass, radiator area, reliability/mission duration, and insolation level are evaluated through several CBC parametric case studies. These cases include: (1) a 500 We power system for deep space probes; (2) a 50 kWe solar dynamic system for earth orbit and other applications; (3) a 100 kWe man-rated lunar/Mars stationary /rover power system; (4) a 200 to 825 kWe power system for the lunar outpost; and (5) 3300 kWe modules for interplanetary propulsions.

Reserch and Development on Optimalizing Control of Air-Conditioning System : Part 4-Softwares and Actual Results on Optimization for Thermal Storage Operation and Selection of Heat Source

Reserch and Development on Optimalizing Control of Air-Conditioning System : Part 4-Softwares and Actual Results on Optimization for Thermal Storage Operation and Selection of Heat Source

On the vector optimization of heat exchange.

The possibility of improving the match between an energy source and an energy sink in an energy exchange system has been investigated to maximize both energy conservation and economic benefit. Trade-off curves between the total dissipation of available energy (exergy) and the total area of heat exchangers in the system have been obtained under three situations. In the first problem it is assumed that any heat source, of whatever quality and quantity, can be used for heat exchange. In the second problem available heat sources are specified and then the network of heat exchangers is synthesized. In the last problem, sizing of each heat exchanger is considered under the specified heat sources and heat exchanger network. Comparison of these trade-off curves suggests that an appropriate heat source or sources should be chosen by solving the heat source selection problem before the synthesis or design of a heat exchange system is carried out.