A new approach to heat and moisture regeneration in the ventilation system of rooms. II. Prototype of the real device

This paper presents the results of investigations conducted on the real prototype of a regenerator whose operating conditions depended on the weather conditions during the testing (winter of 2004). It has been shown that the heat and moisture recovery coefficients can be purposefully and independently regulated over a wide range by selecting the quantity of the adsorbent and heat-accumulating medium. The use of the proposed device in the ventilation system of a standard two-room apartment under the conditions of Novosibirsk can lead to a 44% reduction of heating costs annually. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 3, pp. 151–157, May–June, 2006.     

Determination of the kinetic curves of drying of blocks of adsorbents-dessicants with different cross sections of channels and of a granulated adsorbent on a change in the flow velocity

The kinetics of convective drying (regeneration) of different types of adsorbents-dessicants with different geometric parameters has been studied. It is shown that adsorbents of a “channel” (cellular) type have a long constant-rate stage of drying, whereas a granulated polydisperse adsorbent is mainly dried at a variable rate. Adsorbents having a maximum water yielding capacity have been revealed. It has been established that the velocity of a drying gas flow substantially influences the process of moisture extraction from all types of adsorbents. In order to describe the kinetic curves of the given phenomenon, a model of a relaxation kinetic equation that quite satisfactorily describes the kinetics of drying of the adsorbents studied was used. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 65–68, January–February, 2009.     

The effect of humidity on friction and wear of an aluminium–silicon eutectic alloy

The sliding wear of an aluminium–silicon eutectic alloy against cast iron counterface in 3–100% relative humidity range has been investigated. The results show that the moisture content has a significant effect on the friction and wear of the Al–Si alloy. The wear rate decreases by two orders of magnitude as the relative humidity increases from 3% to 100%. At low humidity conditions adhesive wear is predominant, whilst at high humidity conditions a layer of compacted oxide–metal debris film is formed on the Al–Si slider surface, which reduces the direct metal–metal contact. The friction coefficient is maximum at 3% and 100% relative humidity conditions. This revised version was published online in November 2006 with corrections to the Cover Date.     

Mathematical model of heat transfer in the U-shaped block of the unpressurized device compartment of a geostationary spacecraft

A new dynamic mathematical distributed-lumped parameter model of heat transfer in the U-shaped block of the service-system module of the unpressurized device compartment of a promising geostationary orbiting spacecraft having a long service life is proposed. A computational algorithm and software for calculating the multidimensional nonstationary temperature fields arising in the process of operation of the airborne-equipment devices and the system of nonregulated heat pipes in the indicated block have been developed. Results of calculation of these fields are presented. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 6, pp. 9–17, November–December, 2007.     

Apatite-forming ability of Ti–15Zr–4Nb–4Ta alloy induced by calcium solution treatment

Ti–15Zr–4Nb–4Ta alloy free from cytotoxic elements shows high mechanical strength and high corrosion resistance. However, simple NaOH and heat treatments cannot induce its ability to form apatite in the body environment. In the present study, this alloy was found to exhibit high apatite-forming ability when it was treated with NaOH and CaCl₂ solutions, and then subjected to heat and hot water treatments to form calcium titanate, rutile, and anatase on its surface. Its high apatite-forming ability was maintained even in 95% relative humidity at 80°C after 1 week. The surface layer of the treated alloy had scratch resistance high enough for handling hard surgical devices. Thus, the treated alloy is believed to be useful for orthopedic and dental implants.     

The effect of frequency of vibration and humidity on the stick–slip amplitude

This work examines the variation of stick–slip amplitude with the variation of frequency of vibration and relative humidity on a mild steel disc. A pin-on-disc machine, developed by the authors, capable of vibrating the disc at different frequency is used for the experiments. During the experiments, normal load, speed, relative humidity and frequency of vibration were varied. The results reveal that, depending on the conditions, a different stick–slip behavior can arise in the same system. It is found that the rate of reduction of stick–slip amplitude has a particular relationship with the frequency of vibration and the relative humidity. It is also observed that the transition from irregular to regular stick–slip behavior is load dependent, while the transition from irregular to smooth sliding is load independent.     

Portable power source based on air-hydrogen fuel cells with free-breathing cathodes

Portable power source based on air-hydrogen fuel cells (FCs) operating in a free-breathing cathode regime has been developed. At a volume of 100 cm³, the source has a power capacity of 8.5 W h and generates a power of 2 W that is independent of the temperature within 5–40°C and the relative humidity of the ambient air within 40–98%. With respect to the specific energy characteristics, the proposed PTI type device exceeds other air-hydrogen FCs and in some respects is even superior to power sources based on air-methanol FCs.     

Hydrodynamics and heat transfer in cooling systems with intersecting channels. 3. Effect of the angle of flow and the number of stages

Results of further investigation of some variants of wafer structures are given. The effect of the angle of flow on the hydraulic resistance and heat transfer at Re numbers of 1·10²–2·10⁴ is revealed. The temperature field of a two-stage system is analyzed. It is shown that a size reduction of the structure and an increase in the number of stages make it possible to obtain the maximum possible coefficient of reduced heat transfer (2.5–2.8)·10⁵ W/(m²·K). Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 2, pp. 214–223, March–April, 2000.     

Drying shrinkage of cement paste as measured in an environmental scanning electron microscope and comparison with microstructural models

A recently developed image-intensity-matching technique has been used to analyse images of cement paste which were dried in an environmental scanning electron microscope. Shrinkage that occurs during changes in relative humidity is reported, together with some of the influences of water-to-cement ratio, temperature and age. Results from microstructurally based models are compared with experimental results. The best fit of models to experiment is achieved if calcium silicate hydrate (C–S–H) is divided into two types: high density C–S–H, which does not shrink, and low density C–S–H, which does shrink. Approximate values of unrestrained shrinkage of the low density C–S–H are attained as a function of relative humidity. This revised version was published online in November 2006 with corrections to the Cover Date.     

Simulation of the heat transfer of a lithospheric platform in the subduction zone. II. Method of solution and results of calculations

Based on the control volume method, a numerical algorithm is developed for solving the problem of natural convective heat exchange in the earth's upper mantle. Part I was published in Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 1, pp. 16–25 (1996). Khabarovsk Polytechnic Institute, Khabarovsk, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 2, pp. 261–271, March–April, 1996.     

Proton conductivity of biopolymer–platinum nanoparticle composite under high humidity

A κ-carrageenan–Pt nanoparticle composite (Cg–Pt) was synthesized and its proton conductivity was examined by a complex-plane impedance method. The synthesized Cg–Pt was characterized by transmission electron microscope (TEM) observation, powder X-ray diffraction (XRD), Fourier transformed infrared (FT-IR) absorption measurements, and thermogravimetry/mass spectrometry (TG/MS) analysis. It was revealed that the a.c. electrical conductivity of Cg–Pt strongly depends on relative humidity (RH) and exceeds the conductivity of Cg under conditions of high humidity. From the temperature dependence of the a.c. conductivity, activation energies for protonic conduction were estimated to be 0.47 and 0.34 eV for Cg–Pt and Cg, respectively. The origin of the differences in the conductivities and activation energies are discussed.     

Natural convection of an electrically conducting fluid in a spherical layer. 1. Formulation of the problem

Natural-convection heat transfer of an electrically conducting fluid in a spherical layer modeling the earth’s liquid core is considered. The effect of different physical factors on fluid flow in a spherical interlayer is analyzed. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 5, pp. 850–854, September–October, 1998.     

Fabrication of a CuO-infiltrated ZnO composite and its gas sensing properties

CuO–ZnO composites were fabricated by heating with infiltrating a cupric solution into a porous ZnO matrix. The composites possess a nonlinear, rectifying current–voltage character due to the presence of a p–n junction produced by the CuO and ZnO semiconductors. This junction is essential for the creation of voltage-dependent sensing properties of humidity and flammable gases. The forward current (CuO: positive bias) greatly increased with increasing the relative humidity, while the reverse current only slightly increased with an equivalent increase in the relative humidity. This asymmetric current change with the humidity is similar to that observed for conventional CuO and ZnO sintered specimens heterocontact produced by mechanically pressing the specimens together. The current was increased by the introduction of CO and H2 (4000 p.p.m.) at 250°C, with the current increase due to CO exceeding that of the H2 in the measured bias region within ±6 V. The utility of the new processing method for forming p–n semiconductor junctions open to the atmosphere has been shown. This revised version was published online in November 2006 with corrections to the Cover Date.     

First-Principles Calculation of the Air–Water Second Virial Coefficient

Recent theoretical work has produced quantitatively accurate potential-energy surfaces for water with common gases. These pair potentials have been used to calculate second interaction virial coefficients with an accuracy superior to that obtained by most experiments. In this work, results for water–nitrogen, water–oxygen, and water–argon are combined to calculate an effective second virial coefficient for water with air. The results are in agreement with the existing experimental data, but they cover a wide range of temperatures while the experimental data extend only from 253 to 348 K. These results will be useful for humidity standards and other applications requiring thermodynamic properties of moist air.     

Calculation of the effect of evaporating drops on the relative law of heat exchange with a disperse mist flow

On the basis of a two-layer scheme of wall turbulence, a relative law of heat exchange with a disperse mist flow is calculated. It is shown that the influence of drops on heat exchange leads to a finite “stepwise” increase in heat transfer compared to the case of a single-phase vapor flow. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 3, pp. 510–513, May–June, 1997.     

Development of microwave assisted zeolite–water adsorption heat pump

A microwave assisted zeolite–water adsorption heat pump system was designed, manufactured and investigated experimentally. The influence of operation time of microwave oven on performance of the adsorption heat pump was studied. The performance criteria: coefficient of performance, specific cooling power and volumetric cooing power, were calculated for the designed and tested adsorption heat pump system. The regeneration of adsorbent bed was achieved very rapidly (35 min) by using microwave heating system. The poor thermal conductivity of adsorbent did not affect the periods of isosteric heating and isobaric desorption processes.     

Specific features of the oxidation of complex titanium alloys in the as-cast and recrystallized states

We study the heat resistance of complex titanium alloys with 4.5–11 wt.% Al in the as-cast and recrystallized states at a temperature of 800°C for 50 h. It is shown that the procedure of alloying has the same influence on the as-cast and recrystallized metals, and the initial structure affects the kinetics of oxidation of the latter. In this case, the ground recrystallized structure promotes the formation of oxide films with high adhesive strength guaranteeing high levels of the heat resistance of the alloy for long periods of holding. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 3, pp. 112–117, May–June, 2008.     

An analysis of the sensitivity of planar capacitive humidity converters

A solution of the problem of analytically estimating the change in the sensitivity of planar capacitive humidity converters by modeling the nonuniform electric field in the monitored volume of the material with a nonuniform humidity distribution is considered. __________ Translated from Izmeritel’naya Tekhnika, No. 9, pp. 67–70, September, 2006.     

Medical instrument based on a heat pipe for local cavity hypothermia

The design and results of tests of an instrument based on a heat pipe for local cavity hypothermia are presented. The instrument is a part of a device for noninvasive nonmedical treatment of inflammatory diseases of the organs of the small pelvis, pathologies of alimentary canal, etc. Academic Scientific Complex “A. V. Luikov Heat and Mass Transfer Institute, Academy of Sciences of Belarus,” Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 3, pp. 382–385, May–June, 1996.