Increase In Heat Production Rate Research Articles

Geothermal energy extraction in CO2 rich basin using abandoned horizontal wells

Compared with traditional oil and gas resources, geothermal energy processes the advantages of zero emission, low investment and high productivity, etc. in this paper, a model is developed for simulating CO2 circulating in a geothermal horizontal well. The energy and momentum balance equations of CO2 flow in long tube and annuli are solved numerically. The relationships between geothermal productivity and injection parameters are revealed. It is concluded that: (a) The standard of choosing parameters for measuring the rate of geothermal production is whether or not the parameter can reflect the heat transfer rate or fluid temperature rise. (b) Taking multiple factors (temperature decrease, enthalpy decrease, small increase in heat production rate and increase in cost) into consideration, a small mass injection rate is recommended to obtain a better economic performance. (c) Taking multiple factors (temperature increase, decrease in heat production rate and increase in cost) into consideration, a small injection pressure is recommended to obtain a better economic performance.

Toward a theory of energetically optimal body size in growing animals.

Our objective was to formulate a general and useful model of the energy economy of the growing animal. We developed a theory that the respiratory energy per unit of size reaches a minimum at a particular point, when the marginal respiratory heat production rate is equal to the average rate. This occurs at what we defined as the energetically optimal size for the animal. The relationship between heat production rate and size was found to be well described by a cubic function in which heat production rate accelerates as the animal approaches and then exceeds its optimal size. Reanalysis of energetics data from the literature often detected cubic curvature in the relationship between heat production rate and body size of fish, rats, chickens, goats, sheep, swine, cattle, and horses. This finding was consistent with the theory for 13 of 17 data sets. The bias-corrected Akaike information criterion indicated that the cubic equation modeled the influence of the size of a growing animal on its heat production rate better than a power function for 11 of 17 data sets. Changes in the sizes and specific heat production rates of metabolically active internal organs, and body composition and tissue turnover rates were found to explain notable portions of the expected increase in heat production rate as animals approached and then exceeded their energetically optimum size. Accelerating maintenance costs in this region decrease net energy available for productive functions. Energetically and economically optimum size criteria were also compared.

The effect of changes in salinity on the energy yielding processes of Chlorella vulgaris and Dunaliella maritima cells

The unicellular green halotolerant microalga Dunaliella maritima grown in medium containing 500 mM NaCl and the freshwater microalga Chlorella vulgaris were used as model systems to study adaptation of energy yielding mechanisms of cells in culture to changes in salinity. A microcalorimetric method was used to study the alteration of the heat production rate of microalgae depending on the salt content in the culture medium. It was shown that the heat production of Chlorella at low salt concentration (50 mM) increased and that it decreased at high concentration (500 mM). Chlorella was unable to adapt to concentrations of 1 M NaCl and above—in this sense, this degree of salinity was a critical value for the adaptive processes of this microalga. On the other hand, the halotolerant Dunaliella readily adapts to very high salinity. At 1.5 M salt concentration there was a considerable increase in heat production rate up to 200% compared with the 500 mM control. The light reactions of the microalgae in salinity were measured by a photo-microcalorimetric method. Dunaliella cells absorbed heat to a greater extent than Chlorella vulgaris cells which can be interpreted as more stored light energy in photosynthate. A polarographic method with a Clark-type electrode was employed in the dark to determine the respiration rate from the oxygen uptake rate; and photosynthesis was determined in the light from the oxygen evolution rate. At a salt concentration of 50 mM, there was some increase of the oxygen uptake rate by Chlorella cells and at high concentrations of salt in the medium from 500 mM to 1 M there was a sharp inhibition of this process. Dunaliella cells gave a different response to increasing salt concentrations in terms of the oxygen uptake rate. It considerably increased by 50–60% compared when the salt concentration in the medium was increased to 1.5 M. It is interesting to see that the rates of energy yielding processes in the Dunaliella control cells were significantly higher than those of Chlorella cells, presumably because of the increased rate of pumping out Na + ions. The data support the hypothesis that an important feature of salt sensitive and salt tolerant microalgae is the increased energetic rate which ensures a quick and effective adaptation of them to stress.

Characterizing critical phases of germination in winterfat and malting barley with isothermal calorimetry

The heat production of seeds during germination comes from metabolism as well as hydration. Previous studies either lack continuous measurements, or are based on samples composed of more than one seed, thus failing to characterize differences among the critical phases of germination. This study examines the potential of isothermal calorimetry to characterize water uptake and metabolism in single seeds. Seeds of malting barley (Hordeum vulgare L.) and winterfat [Krascheninnikovia lanata (Pursh) A.D.J. Meeuse & Smit], two species with contrasting seed size, structure, composition and selection history, were used to determine patterns of heat production rate by isothermal calorimetry during water uptake and germination. Embryos of malting barley contributed less than 4% of total seed weight, and metabolic heat production during Phase I of germination was negligible compared to that due to hydration. Embryos accounted for 74% of seed mass for winterfat, and the majority of heat produced in Phase I was due to metabolic heat release. The total heat production rate in Phase I decreased rapidly in malting barley due to slowing of hydration reactions, but increased gradually in winterfat due to an increasing metabolic rate. The heat production rate at the end of Phase II was about twice as high in malting barley as in winterfat. This indicates a higher metabolic activity for malting barley than for winterfat seeds during germination, which may have also contributed to the rapid increase in the heat production rate of malting barley seedlings during Phase III, compared to the gradual increase in heat production rate of winterfat. The comparison between excised embryos and intact seeds indicates that the covering tissues delay radicle emergence in malting barley, but not in winterfat, due to differences in seed structure between the two species.

Effect of gentamicin on human blood cells metabolism as measured by microcalorimetry.

The effect of gentamicin on overall metabolism in human blood cells was studied by microcalorimetry. At concentrations above therapeutic levels, the drug induced an increase in heat production rate in red cells, whereas no effect was found at lower concentrations. The Na/K-pump was unaffected at any gentamicin concentration. A slight increase in heat production rate was noted in granulocytes when incubated with gentamicin at concentrations above therapeutic levels, otherwise no effect was recorded at lower concentrations. Lymphocytes were unaffected by gentamicin at any concentration. Microcalorimetry seems to be a suitable method for studying the effect of drugs on overall cell metabolism, and for evaluating the Na/K-pump activity.

Calorimetric study on human erythrocyte glycolysis. Heat production in various metabolic conditions.

The heat production of human erythrocytes was measured on a flow microcalorimeter with simultaneous analyses of lactate and other metabolites. The heat production connected with the lactate formation was about 17 kcal (71 kJ) per mol lactate formed which corresponded to the sum of heat production due to the formation of lactate from glucose and the heat production due to neutralization. The heat production rate increased as the pH of the suspension increased, corresponding to the increase in lactate formation. Glycolytic inhibitors such as fluoride and monoiodoacetate caused a decrease in the rate of heat production, whereas arsenate induced a large transient increase in heat production associated with a transient increase in lactate formation. Decrease in pyruvate concentration was usually associated with increase in heat production, although the decreased pyruvate concentration was coupled with formation of 2,3-bisphosphoglycerate. When inosine, dihydroxyacetone or D-glyceraldehyde was used as a substrate, an increase in the heat production rate was observed. Addition of methylene blue caused an oxygen uptake which was accompanied by a remarkable increase in heat production rate corresponding to about 160 kcal (670 kJ) per mol oxygen consumed. The value for heat production in red cells in the above-mentioned metabolic conditions was considered in relation to earlier known data on free energy and enthalpy changes of the different metabolic steps in the glycolytic pathway.