Influence Of Dead Volume Research Articles

A field investigation of a solar-powered adsorption cooling system under Guangzhou's climate with various numbers of heat exchangers in the adsorbers

In the current study, a solar-powered double-bed adsorption cooling system has been built and tested in the Guangzhou climate. The effect of the pre-heating process on the cooling performance of the adsorption cooling system powered by solar energy has been experimentally investigated. A specific cooling power of 52.2 W/kg and a coefficient of performance of 0.20 were achieved under a 2-h pre-heating process with operating conditions of 26°C cooling water inlet temperature, 16°C chilled water inlet temperature, 8 L/min hot water and cooling water flow rate, 2 L/min chilled water flow rate and 600 s adsorption/desorption phase time. The average specific cooling power and coefficient of performance were improved by 26.1% and 33.3%, respectively, as compared to the case without conducting the pre-heating process. In addition, the influence of dead volume on the specific cooling power and coefficient of performance of the adsorption cooling system has also been investigated. Using various numbers of heat exchangers in the adsorber achieved different values of adsorber dead volume. The results show that a higher specific cooling power value is obtained with a smaller dead volume. Finally, the cooling performance of the adsorption cooling system was also studied under various operating conditions and a maximum specific cooling power and coefficient of performance are 180.4 W/kg and 0.29, respectively.

A New Correction Method for Oil–Water Relative Permeability Curve on the Basis of Resistivity and Water Saturation Relationship

Oil–water relative permeability curve constitutes important basic data in reservoir engineering. Given the influence of dead volume on experimental apparatus, the actual oil–water relative permeability curve cannot be obtained when the unsteady-state method is adopted to measure oil–water relative permeability. In this paper, on the basis of the analysis of the influence of dead volume on oil–water relative permeability, we summarize the conventional methods used to overcome dead volume and then propose the use of relationship theory between resistivity and water saturation to calibrate the oil–water relative permeability curve. This method mainly aims at to measure the resistance values at both ends of the core by using a resistance-measuring instrument. Meantime, the Archie formula is used to calibrate the relational expression of core resistivity and water saturation based on the steady-state experimental method. Therefore, the core of the actual cumulative oil production and the average water saturation can be calculated, and then oil–water relative permeability can be accurately computed without the influence of dead volume. By comparing the oil displacement process of dead volume calculated through two different methods (probability subtraction and resistivity methods), the crude oil in dead volume is found to be displaced at the beginning of the displacement. The oil–water relative permeability curve corrected through resistivity method can eliminate the influence of dead volume and iterative error in calculation, and is consistent with the law of the actual development of oilfield, which has certain theoretical and practical application values.

Prospects of endogenous carbon monoxide (CO) measurements in exhaled air

Summary. Unlike СО2 at successive breath-holdings, with increasing time, CO concentration aspires to some equilibrium value (to equilibrium concentration) depending on carboxyhaemoglobin content in blood. It is shown that lung diffusion capacity, measured by rate of CO concentration increasing in alveolar volume, approximately twice exceeds total lung diffusion capacity measured by known single breath method, i.e. corresponds to diffusion capacity of alveolar-capillary membrane. On base of mathematical modeling of CO gas exchange process in lung of man, the formula was derived for calculation of integral measured CO concentration in exhaled air, taking into account influence on measuring results of dead (anatomic and device) volume. Influence of dead volume was considered in assumption that in it there is no gas exchange, but in exhaled air volume from it at first passes CO containing in inhaled air, and after CO from exhaled part of alveolar air. Taken into account, that at start of inspiration, dead volume filled by final portion of alveolar air entering to it as a result of previous expiration. Two models were considered: the linear model (LM) when CO gas exchange in changing alveolar volume takes place at constant transfer coefficient and the model of elastic membrane (MEM) when transfer coefficient at breathing is changed in proportion to membrane surface area and in inverse proportion to its thickness. As a result of data analysis it is shown that calculations in MEM approach describe experimental data more adequately and can be used for the solution of the reverse task, i.e. calculation of alveolar-capillary membrane diffusion capacity, lung alveolar volume and equilibrium CO concentration, using three values of measured CO concentration at various breathing regimes. Thus, proposed method, unlike single breath, allows to determine indicated impotent physiological parameters without using of test gas mixtures.