Influence Of Heat Capacity Research Articles

Экспериментальные исследования теплового режима в слоях дорожного покрытия магистральных лесовозных дорог

Economic and social development of both the country as a whole and its individual regions is impossible without maintaining the required level of development and technical condition of the road network. This also applies directly to agricultural producers. Despite the fact that considerable funds are allocated for the construction and repair of roads, the service life of roads often does not meet the standard values. One of the reasons for the low service life of road structures are design errors related to the lack of data on the thermal conductivity of road construction materials, seasonal freezing of the roadbed, which together with unsatisfactory soil and hydrological conditions contribute to significant deformations. One of the main problems in the road industry at present is insufficient consideration of soil and hydrological conditions of the area, which are estimated approximately from topographic maps and materials of old documents or, at best, from the results of reconnaissance surveys. At the same time, it is often difficult to provide the required load-bearing capacity and frost resistance of road structures with an unsuccessfully selected, even short route, since when designing the roadbed, soil and hydrological conditions are secondary, and the choice of the route location is primary. It is well known effect when periodic freezing and thawing of the road surface leads to the appearance of alternating stresses, which significantly accelerate the destruction of the road surface and sometimes the foundation. A thorough understanding of the processes of freezing and thawing of the roadbed makes it possible to avoid design errors, and the significant financial losses associated with them, in the construction of long-distance forest roads. The article presents the features of processes occurring in the layers of road construction during seasonal freezing. Hypotheses about the processes of moisture migration in seasonally frozen soils, the influence of heat capacity and thermal conductivity of road construction materials on the course of these processes, as well as methods for modeling processes occurring in road structures under the influence of natural and climatic conditions are considered, and the results of the field experimental studies are presented.

Study on the Influence of Borehole Heat Capacity on Deep Coaxial Borehole Heat Exchanger

Based on a semi-analytical model established previously for heat transfer in coaxial borehole heat exchangers, the influences of the heat capacities of different parts of the borehole (fluid, pipes and grout) on the performance of deep coaxial borehole heat exchanger (DCBHE) are analyzed. The results are as follows: the heat transfer performance of DCBHE will be underestimated if the heat capacities of different parts of the borehole are ignored; the influences of the heat capacities of different parts of the borehole on the performance of DCBHE are more obvious in the early stage, and gradually weaken with the increasing of time; among the heat capacities of different parts of the borehole, the influence of the fluid heat capacity on the performance of DCBHE is the greatest, and the influence of the pipe heat capacities is the least. Under the working condition studied in this paper, the results obtained with considering the heat capacities of different parts of the borehole are compared to ones ignoring heat capacities of selected elements. It was found that ignoring the fluid heat capacity led to a 0.29 °C lower estimated outlet fluid temperature after 60 h. Omitting the heat capacities of pipes and grout gave 0.03 °C and 0.13 °C lower outlet fluid temperatures after 60 h, respectively. The larger the borehole radius, the greater the influence of borehole heat capacity. The geothermal gradient has little effect on the influence of borehole heat capacity on the performance of DCBHE. The results show that the heat capacities of different parts of the borehole have important effects on the performance of DCBHE, especially in the early stage and for a large borehole radius.

Effects of biofuels properties on aircraft engine performance

Purpose – The purpose of this paper is to examine the effects of heat capacity and density of biofuels on aircraft engine performance indicated by thrust and fuel consumption. Design/methodology/approach – The influence of heat capacity and density was examined by simulating biofuels in a two-spool high-bypass turbofan engine running at cruise condition using a Cranfield in-house engine performance computer tool (PYTHIA). The effect of heat capacity and density on engine performance was evaluated through a comparison between kerosene and biofuels. Two types of biofuels were considered: Jatropha Bio-synthetic Paraffinic Kerosene (JSPK) and Camelina Bio-synthetic Paraffinic Kerosene (CSPK). Findings – Results show an increase in engine thrust and a reduction in fuel consumption as the percentage of biofuel in the kerosene/biofuel mixture increases. Besides a low heating value, an effect of heat capacity on increasing engine thrust and an effect of density on reducing engine fuel consumption are observed. Pr...

The influence of heat capacity and its spatial distribution on the transient wall thermal behavior under the effect of harmonically time-varying driving forces

An analysis was developed for the theoretical investigation of heat capacity and of the effects of its spatial distribution on the thermal behavior of structural walls of uniform thermal resistance. The numerical solution of the governing differential equations under the appropriate initial and boundary conditions, allows the prediction of the time-varying heat flux during the transient heating of walls until quasi steady-state conditions are developed asymptotically. It is derived that as far as the fundamental physical behavior of a clear wall section is concerned, although the time depended heat flux is effectively damped and phased out as the wall heat capacity increases, the average quasi steady-state heat flux is constant, irrespectively of wall heat capacity, incident solar radiation intensity, radiation absorption at the exterior wall surface and particular weather conditions defining wall heat loss or gain. However, even though the average quasi steady-state heat flux is constant irrespectively of the wall heat capacity, its time depended value during the development of transient is strongly influenced by the spatial distribution of heat capacity at a direction perpendicular to the wall plane, something which is determined by the wall time constant.

Influence of heat capacity of a vessel wall and of the heat currents in it on the characteristics of convection in a closed volume

The author analyzes the influence of the wall heat capacity and of the heat currents in it on the characteristics of convective heat transfer in a cylindrical vessel with hemispherical ends.