Central Air Conditioning Systems with Partial Indirect Evaporative Cooling and Utilization of Cold and Heat of Ventilation Emissions

A promising trend in air conditioning systems is the use of indirect evaporative cooling, but in the classic version it is effective in dry and hot climates. For the need to maintain comfortable air parameters in public buildings, it is not possible to fully implement such a process in the conditions of Ukraine (the relative humidity of the outside air ranges from 63 to 75 %). The aim of the work is to increase the energy efficiency of air conditioning systems with standard equipment through partial evaporative cooling and use for cooling water in cooling towers of the air removed from the rooms during the warm season, and in the cold season - use of the exhaust air for preheating the supply air in heat exchanger. A corresponding system diagram was developed and computational studies of a direct-flow circuit and a circuit with recirculation were carried out for one of the educational buildings of the Igor Sikorsky Kyiv Polytechnic Institute. According to the results of calculating the direct-flow circuit in the warm period, the energy efficiency of indirect evaporative cooling was 23.5 %. The annual amount of recovered heat of ventilation emissions for this scheme in the cold period was 3731 GJ / year, and the economic effect - 1473185 UAH / year. For a circuit with recirculation during a warm period, the greatest effect of indirect evaporative cooling is achieved with a recirculation rate of 10 %, and for the overall decrease in the cooling capacity of the air conditioner during this period the greatest impact is not indirect evaporative cooling, but recirculation. In the cold season, the greatest utilization effect is also achieved with a 10 % recirculation rate.

Analytical Method of Human Systemic and Global Circulation

The human circulatory system is one of the admirable rhythms of nature. The heart and the vasculature are constitutive structures. The vasculature consists of arterial and venous appurtenances which are arranged in an idealized network capable of enhancing circulation. The crux of this study is the representation of the cardiovascular system as a network in which electrical constraints apply. As a network, the system is amenable to graph analytic treatment; as edge-nodal parameters ensue, topological constraints apply. In virtue of cardiac auto-rhythmicity, electrical impulses are driven through the vessels to the body cells. As a rule, the vessels must elicit a modicum of resistance. This work weaponized the elements of graph theory and electrical properties of the heart in elucidating the flow mechanism associated with the cardio-vascular system. The voltage drop across the connecting vessels (idealized as wires) was carefully depicted and analyzed by the method of matrices. When the cardiac function is within physiological definition a vascular compartment may be a liability in the event of poor circulation. Therefore the knowledge of vascular resistive capacities, which this work portrayed, is a sine-qua-non to the assessment of flow integrity of the system under consideration. MSC 2010 No.: 05C21, 92C42, 92B25. Keywords: Cardiovascular, Network, Matrices, Flow, Circuit, Edges and Nodes, Wave propagation, Bifurcation.

Drug-Coated Balloon for Arteriovenous Access Stenosis in Hemodialysis Patients

Hemodialysis access stenosis is a pervasive problem that occurs due to the physiology of the high-flow circuit. Stenosis occurs due to endothelial and smooth muscle injuries that result in neointimal hyperplasia. Percutaneous transluminal angioplasty is the standard treatment for dialysis access-induced stenosis. Unfortunately, it is also associated with vessel wall trauma, which causes further intimal hyperplasia and restenosis. Data from randomized controlled trials (RCTs) and systematic reviews of the use of drug-coated balloons (DCBs) for dialysis access stenosis have been controversial. While several single-center trials or RCTs have reported safe and effective use of DCBs, conflicting results still exist. Furthermore, paclitaxel is known to be associated with an increased mortality risk. Herein, we review the current evidence on the role of DCBs in the treatment of dialysis access stenosis.

CORRECTION OF THE QUALITY OF CURRENT OF THE ELECTRIC NETWORK WITH A THYRISTOR REGULATOR OF AC VOLTAGE WITH ACTIVE-INDUCTIVE LOAD

The use of the AC voltage control method is considered. In this method, the improvement of the current quality of the supply network is achieved by a discrete change of the inductance in the network current flow circuit. In this method, it is proposed to use a circuit with counter-parallel thyristors and the neutral wire. The dependences of the harmonic coefficient and the current distortion coefficient of the electric network on the values of the regulated voltage are constructed. The obtained dependences prove the effectiveness of the proposed regulator. The required number of reactor sections is determined and the proper inductance of their windings to provide the values ​​of the harmonics coefficient that does not exceed 7% while adjusting the voltage depth of 50% on the active-inductive load. References 9, 3 figures 3, table.

Optimization of online particle counting with a 3D-printed bubble trap

Particulate evaluation is needed for the approval of cardiovascular devices. Air bubbles lead to higher particle counts when light obscuration method (LOM) is used. The aim of the study was to test a custom made bubble trap that removes air bubbles (2 - 100 μm) from a flow circuit prior to online particle counting. Artificially generated air bubbles were counted with an online particle counter with and without the bubble trap. Air bubbles were reduced by about 71 % to 91 % by using the bubble trap.

Major and minor head losses in a hydraulic flow circuit: experimental measurements and a Moody’s diagram application

Domestic and industrial hydraulic drainage networks have gradually become more complicated because of the cities’ rapid expansion. In surcharged hydraulic systems, the head losses may become rather significant, and should not be neglected because could result in several problems. This work presents an investigation about major and minor head losses in a hydraulic flow circuit, simulating the water transport in a drainage network at room temperature (298.15 K) under atmospheric pressure (101,325 Pa). The losses produced by the fluid viscous effect through the one used cast-iron rectilinear pipe (RP-11) and the localized losses generated by two flow appurtenances, one fully open ball valve (BV-1) and one module of forty-four 90º elbows (90E-8) were experimentally measured. Experimental data generated head-loss curves and their well fitted to potential regressions, displaying correlation coefficients (R2) of 0.9792, 0.9924, and 0.9820 for BV-1, 90E-8, and RP-11, respectively. Head loss experimental equations and local loss coefficients through BV-1 and 90E-8 were determined successfully. The Moody’s diagram application proved to be a quite appropriate tool for an approximate estimation of Darcy-Weisbach friction factor. A good approximation between friction factor values obtained via experimental measurements and the Moody’s diagram was observed with mean absolute deviate of 0.0136.

Voltage mapping to guide pacemaker placement in patients with CHD

Transvenous pacemaker implantation for sinus node dysfunction in patients with Fontan palliation presents the difficulty of finding suitable pacing tissue and the potential of causing vascular obstruction in a low-flow circuit. We describe a patient who underwent electro-anatomic voltage mapping to guide a transvenous single chamber lead within her Fontan baffle. This highlights the use of advanced mapping technologies for pacemaker implantation in complex cyanotic heart disease.

3D Encapsulation Made Easy: A Coaxial-Flow Circuit for the Fabrication of Hydrogel Microfibers Patches

To fully exploit the potential of hydrogel micro-fibers in the design of regenerative medicinal materials, we designed a simple, easy to replicate system for cell embedding in degradable fibrous scaffolds, and validated its effectiveness using alginate-based materials. For scaffold fabrication, cells are suspended in a hydrogel-precursor and injected in a closed-loop circuit, where a pump circulates the ionic cross-linking solution. The flow of the cross-linking solution stretches and solidifies a continuous micro-scaled, cell-loaded hydrogel fiber that whips, bends, and spontaneously assembles in a self-standing, spaghetti-like patch. After investigation and tuning of process- and solution-related parameters, homogeneous microfibers with controlled diameters and consistent scaffolds were obtained from different alginate concentrations and blends with biologically favorable macromolecules (i.e., gelatin or hyaluronic acid). Despite its simplicity, this coaxial-flow encapsulation system allows for the rapid and effortless fabrication of thick, well-defined scaffolds, with viable cells being homogeneously distributed within the fibers. The reduced fiber diameter and the inherent macro-porous structure that is created from the random winding of fibers can sustain mass transport, and support encapsulated cell survival. As different materials and formulations can be processed to easily create homogeneously cell-populated structures, this system appears as a valuable platform, not only for regenerative medicine, but also, more in general, for 3D cell culturing in vitro.