HVAC&R

This paper discusses the suitability of HFC-161 over other refrigerants. Apart from having zero ODP and GWP value of 12, HFC-161 refrigerant can prove a promising alternative to HCFC-22 and various other HCFC refrigerants facing the fate of phase out. Various results are obtained on the basis of COP, discharge temperature, cooling capacity and power consumption. The general finding shows that HFC-161 refrigerant gives better COP, increased refrigeration effects and lower discharge temperatures. The flammability of HFC-161 needs to be addressed while using in air conditioner. A 1.5 TR capacity DC inverter operated air conditioner is to be tested in psychometric test laboratory for Capacity rating and Power consumption test.

Kondensor merupakan komponen vital dari sistem pendingin udara (AC) yang berfungsi untuk mengkondensasi refrigeran. Kondensasi diakibatkan oleh penyerapan panas refrigeran oleh udara yang melewati penukar kalor fin and tube. Tingginya tahanan termal sisi udara oleh karena rendahnya konduktifitas termal menyebabkan rendahnya laju
perpindahan panas. Oleh karena itu, studi ini memfokuskan pada peningkatan laju perpindahan panas konveksi dengan menggunakan longitudinal vortex generator (LVG). Penggunaan vortex generator (VG) berdampak pada peningkatan pressure drop. Untuk mengatasi masalah ini, eksperimen dilakukan dengan menempatkan enam silinder yang
dipanasi di dalam saluran persegi empat. Perbaikan laju perpindahan panas dari silinder ke udara dilakukan dengan menempatkan VG berlubang pada permukaan plat. Susunan VG, jumlah pasang dan kecepatan aliran udara masuk divariasikan. Hasil penelitian
menunjukkan bahwa kenaikan laju perpindahan panas dan pressure drop tertinggi dihasilkan oleh perforated concave delta winglet (PCDW) tiga pasang staggered dengan nilai berturut-turut 46,3% dan 87,5%.

Ground-coupled heat pumps are highly efficient HVAC systems that provide heating and cooling for buildings. The high initial cost of drilling boreholes is one of the primary reasons that limit the widespread application of a ground-coupled heat pump. It is very important to develop ...

Prismatic glazing is found in many building applications, such as complex fenestration systems to control solar heat gains and glare and re-direct sunlight to building interior spaces and daylighting (and lighting) systems to enhance their optical and lighting performance. However, modeling and simulation of such prismatic glazing has been a very difficult task due to its versatile and complex geometrics. This article presents the development and validation of a simplified model to compute the optical characteristics and dominant directions of the transmitted and reflected beam rays of sawtooth-like prismatic glazing. The model was based on tracing the average ray and was extensively validated using third-party data derived from ray tracing computer simulations and measurement using integrating spheres and goniophotometers. The model's predictions for the transmittance and reflectance of single and double prismatic panes compared well overall within the accuracy of the third-par...

This study investigated experimentally the effects of real fouling material at the air side of the evaporator's heat exchanger coil on the performance of room air-conditioner units as well as the impact of some fouling material compositions on indoor air quality. At the end of the ...

ABSTRACT This article assesses the most common architectural and environmental strategies in Ghadames housing in Libya. Preliminary data were collected through field surveys undertaken in July 2013, the hottest and driest season in Ghadames. The surveys investigated the indoor thermal environment and efficiency of energy use in Ghadames housing. The actual mean vote scale was used to investigate occupants’ thermal feeling coupled with recording physical environment and also actual measurements of a number of existing houses. Additionally, objective surveys were conducted to (a) verify the subjective data, (b) provide an overall view of the residents’ life style in the old town, and (c) understand the most significant techniques employed in old dwellings. The subjective survey “questionnaire” distributed among nine new and eight old houses shows that the majority of respondents is satisfied with the number of architectural issues in modern housing design. This general satisfaction excludes the inherited identity of the traditional architecture embedded within the society. On the other hand, occupants are more satisfied with old buildings in regard to indoor environmental conditions, energy consumption, and construction materials. The occupants of old houses expressed their thermal satisfaction with the indoor comfort conditions, but the predicted mean vote, based on measurements and ISO 7730, implied discomfort (hot).The survey also carried out interviews with a number of locals, underlining their personal impressions and preference toward the change of the existing built environment. Findings indicate that, occupants’ satisfaction and perception toward the built environment have not been achieved in new housing developments of Ghadames owing to the lack of understanding of the sociocultural needs of the local community. In addition, a 3D digital model was created for the old town and imparted a full understanding of the building dynamics and physics, explicating the complexity of the compactness of its urban morphologies. The results also showed subjects were feeling neutral to slightly warm in old buildings even when indoor air temperatures reached 32°C.

An urban energy management tool was developed, which is able to predict the heating energy demand of urban districts and analyze strategies for improving building standards. Building models of different Levels of Detail are investigated and analyzed according to their suitability for forecasting energy demand. Based on the specific 3D city model, an input file is generated, which can be read by the building simulation model. Special focus is put on a method for modeling the heating energy demand of the buildings with the fewest input parameters possible, but one which will give reliable forecast results. A simple transmission heat loss method and an energy-balance method were tested. In both cases, there was a good correlation between the measured and calculated annual values for a case study area of over 700 buildings in Ostfildern, Germany. The results also show that a D city model (with low geometrical detail) can be used for energy demand forecasting on an urban scale.

ABSTRACT An analysis of the ventilation effectiveness of a prototype personalized ventilation system of working places named PERMICS-LOS1 (Personal Microclimate System) was made, based on measurements of the air velocity field and of tracer gas concentrations using the decay method. The emphasis of the analysis was mainly on an experimental verification of a parameter based on the relative decrease of tracer gas concentration in the first minute of system operation dC(1) and on local ventilation efficiency using the local air-change index ∊L.. A system analysis was made for several different operating regimes of personalized ventilation, where changes in air quantity and the direction of supplied air in the breathing zone were applied. The results of the experimental analysis were statistically evaluated, compared, and included in the existing database of previous research for use as supplementary values. The performed analysis has confirmed previous findings as well as the connection between the dC(1) parameter and ventilation effectiveness parameters, especially with the local air-change index.

... The authors are thankful to José Berrondo Mir (Mabe TyP operation's vice president), Agustín Soto (refrigerators engineering's manager), as well as Francisco Antón (I+D manager), for their support to this project, and to the ... 1. Abramson, DS, Turiel, I. and Heydari, A. 1990. ...

ABSTRACT This paper presents a study on HCFC-22 alternative refrigerant mixture flow through capillary tubes, analyzing two different approaches for two-phase flow modeling: separated flow and homogeneous. Simulation results were compared to a large experimental data bank (about 200 different operational conditions/geometries) for R-410A and R-407C flow through capillary tubes for both subcooled and two-phase inlet conditions, obtained in an experimental unit implemented for this study. The comparison showed that both models are suitable for simulation of refrigerant mixture flow in capillary tubes, with the same error level in relation to experimental data.

The cosorption of water vapor and carbon dioxide on BPL activated carbon, silica gel (Grade 40), and 13X molecular sieve were investigated in this study. The explicit analytic equilibrium sorption characteristic equations for cosorption of water vapor and carbon dioxide were obtained from the correlation of experimental data of Hines and Ghosh. The cosorption heats of adsorption were calculated from these equilibrium sorption characteristic equations by applying the method of Sircar. A gas-side-controlled adsorption model, with finite transfer coefficients, for the binary mixture of water vapor and carbon dioxide was derived. In a previous work, the single-blow situation was analyzed illustrating the importance of considering both species simultaneously. This previous work also illustrated that the time scale for CO2 adsorption is much shorter that H2O adsorption. In the present work the model was extended and applied to rotary counterflow regenerative desiccant dehumidifiers, and removal efficiencies were documented, showing the contaminant removal potential of such systems.These results also illustrate that a single desiccant wheel cannot remove both components highly effectively. When the required removal efficiencies are not too high, molecular sieve does have respectable removal efficiencies for CO2 and H2O at lower sorption. However, to have higher removal potentials, a twowheel system appears to be more promising.

Operating rooms often exhibit vertical temperature gradient, radiant asymmetry, local airflows, and local body cooling. The impact of these parameters on the thermal comfort of the occupants can be greatly affected by the type of air-conditioning system used in the room. This work evaluated thermal comfort conditions in an operating room ventilated with a spiral diffuser jet using an instrumented thermal manikin with heated sensors. The objective is to assess the conditions of thermal comfort and local discomfort of the patient and surgical team in this kind of environment using the concept of equivalent temperatures and a manikin with heated sensors. Additionally, the method proposed by Fanger was used to evaluate the thermal sensation. The results showed a very small change in the equivalent temperatures in different parts of the body for the surgeon and nurse. The thermal sensation for the surgeon and nurse simulated by the manikin and using a thermal comfort diagram for equivalent temperature was neutral in the whole body. However, higher equivalent temperatures were found on the heads of the surgeon and nurse because of the heat exchange by radiation from the surgical lights. The local thermal sensation for the patient varied from too cold, cold, and neutral, depending on the body part. Finally, the methodology proposed showed to be very effective for evaluating the thermal comfort conditions in operating rooms when compared to the method proposed by Fanger.

... Among all the refrigerants tested, R-134a had the highest initial absorption rate and solubility in POE under the test conditions. For the blended refrigerants, the differential solubility of individual refrigerant component depended on its par-tial pressure and its vapor pressure. ...

A review of published studies of numerical techniques for air filter performance simulation shows that there are two general approaches to such simulations. One describes gases flowing through filter media as continuous fluids, influenced by the macro properties viscosity, density, and pressure. The alternate approach treats gases as molecules in random motion, impacting their own kind and solid surfaces on a micro-scale. The appropriate form for a given filter medium and operating condition depends on the gas properties and the Knudsen number (Kn) of the smallest fibers in the filter medium simulated. When no fiber Kn exceeds 0.01, the Navier–Stokes equation and finite-volume solutions should simulate filter media pressure drop and particle capture reliably, if correct particle and fiber boundary conditions, including “slip” at boundaries, are employed. In addition, fibrous media geometry must be modeled in enough detail to make simulation results match experimental data. Part I of...