Air Conditioning Applications Research Articles

Microstructure and Magnetic Properties of La-Ca-Sr-Mn-O Perovskite Ceramics

A wide range of di erent types of materials, from metals to ceramics, exhibit the magnetocaloric e ect [1]. Generally, the magnetocaloric e ect manifests itself as a reversible increase in temperature when the magnetic material is placed in a magnetic eld, and the maximum magnetocaloric e ect occurs near the Curie temperature. Magnetic ceramics materials are very stable at room temperature, can be compositionally tuned to adjust the Curie temperature, and do not corrode in water. This makes them an attractive option for use as regenerators for magnetic refrigeration systems. Families of functional materials with a large magnetocaloric e ect have been found in several perovskite type manganese oxides such as Caand Sr-doped lanthanum manganites, La0.67Ca0.33−xSrxMnO3 (x = 0; 0.33) [2]. These samples show a substantial magnetocaloric e ect in a temperature range around their respective Curie temperature, which makes the compounds suitable for air-conditioning and refrigeration applications. By varying the composition parameter x the Curie temperature can be adjusted between 267 K (x = 0) and 369 K (x = 0.33) [2]. In this contribution, the structure, microstructure and the in uence of high pressure oxygenation on magnetisation behaviour of La0.67Ca0.33−xSrxMnO3, prepared by solid state synthesis were investigated.

Pre-industrial development and experimental characterization of new air-cooled and water-cooled ammonia/lithium nitrate absorption chillers

Two pre-industrial prototypes of a new ammonia/lithium nitrate absorption chiller, a water-cooled one and an air-cooled one, have been built and experimentally characterized. The single-effect configuration of the absorption refrigeration cycle was selected for both prototypes in which brazed plate heat exchangers were used in all thermal components. These prototypes, designed for air conditioning applications, were tested under various operating conditions to assess their performance. The water-cooled prototype yields 12.9 kW of cooling capacity and an electrical COPelec of 19.3, when operating at a 15 °C chilled water temperature, 90 °C hot water temperature and a 35 °C cooling water temperature. In the case of the air-cooled prototype, at a 15 °C chilled water temperature, 90 °C hot water temperature and a 35 °C ambient air temperature, the cooling capacity is 9.3 kW and the electrical COPelec is 6.5.

Interaction effects between parameters in a vortex generator and louvered fin compact heat exchanger

Heat exchangers for air conditioning applications are often of the fin and tube type. By choosing special fin geometries, the thermal performance of the heat exchanger can be enhanced. One of the recently proposed fin geometries for round tubes is the combination of louvers with a delta winglet vortex generator (VG). Several parameters impact the performance of this design, such as the louver angle and the angle of attack of the vortex generator. The fin geometry can be optimised by performing numerical simulations for different values of these parameters. Many authors use design of experiments techniques to reduce the number of simulations, such as the Taguchi method. However, this often implies the assumption that interaction effects between the parameters are negligible. In this work, a full factorial analysis is done to resolve all interaction effects. It is shown that there are important interactions between the height of the VG, the aspect ratio of the VG and the louver angle. These interactions are of the same order of magnitude as the main effect of the parameters and are therefore not negligible. Taking these interactions into account, the impact of the parameters on the heat transfer coefficient, the friction factor and the VG-1 performance evaluation criterion (PEC) are mapped. It is shown that the fin pitch is by far the most important parameter. Varying the louver angle, VG aspect ratio, the VG height ratio or the VG angle of attack results in a change of the VG-1 PEC of between 0% and 3.5%, depending on the interaction with other parameters.

Measurements of the isobaric heat capacity of R1234yf in liquid phase at temperatures from 305 K to 355 K and pressures up to 5 MPa

2,3,3,3-Tetrafluoropropene (R1234yf) is an environmentally friendly promising alternative to 1,1,1,2-tetrafluoroethane (R134a) in air conditioning applications. The heat capacity of R1234yf in liquid phase was investigated in this study. The measurements were carried out with a modified heat conduction calorimeter. A total of 74 data points were obtained among 305–355K and 1.5–5MPa. The uncertainty of the heat capacity measurements was estimated to be less than 1.7%. An empirical equation was correlated to reproduce the experimental result with its terms chosen by a stepwise method. The maximum deviation between the correlating equation and the experimental data was 1.5%. Furthermore, saturated liquid heat capacity of R1234yf was obtained by extrapolating the correlation to saturated pressures. Finally, a comparison was done between the present data and literature experimental data and calculations from a fundamental equation of state.

Thermodynamic properties of HFO-1243zf and their application in study on a refrigeration cycle

Thermodynamic properties of HydroFluoro-Olefin, 3,3,3-trifluoropropene (HFO-1243zf) are firstly modeled with an accurate molecular based PC-SAFT equation of state (EOS). The average absolute deviations (AAD) between vapor pressures, saturated liquid densities from this developed PC-SAFT EOS and experimental data are 0.15% and 0.80%, respectively. The average absolute deviations between predicted gaseous pressures, sub-cooled liquid densities from the PC-SAFT EOS and experimental data are 0.91% and 0.92%, respectively. In this study, the developed PC-SAFT EOS for HFO-1243zf and other EOSs for R-134a, R22, and R32 are used in the investigation of a refrigeration cycle for air conditioning application. The results show that cycle using R1243zf as refrigerant has the highest coefficient of performance (COP) and it is a potential candidate for the replacement of R134a in a refrigeration cycle.

In brief

PAGE 786 Research from Pakistan and the UK presents a novel dual-port diversity/MIMO antenna for UWB applications. The system is compact and suitable for non-planar applications as well as being reconfigurable. The MIMO elements can be placed in stacked/back-to-back as well as in orthogonal/around-corner arrangements. Compact and reconfigurable systems (including UWB) are important for Wide Personal Area Networks. PAGE 826 A system that implements a temperature gradient sensor and a beacon signal transmitter has been proposed in work from Spain. The system is fully autonomous and self-powered by energy harvesting from a very low temperature gradient. It was originally conceived to power a low-power satellite beacon and has found applications in automatic air conditioning and heating systems. Novel dual-port diversity/MIMO antenna has potential ultrawide band applications PAGE 833 A novel computational technique to study the terminal influence inside the three-dimensional nano-scale MOSFET using Technology CAD simulations is shown in work from the United States. Within the MOSFET, the derivative of the electrostatic potential can be taken with respect to voltages at each terminal; when these derivatives are summed together, they always sum to unity. These functions can be used to quantify the relative influence or control of terminals anywhere inside the MOSFET, including the channel. Temperature gradient sensor and beacon signal transmitter used in automated air-conditioning and heating systems PAGE 817 Researchers in the United States have demonstrated the first contactless radio frequency (RF) probes for on-wafer characterisation of microwave integrated circuits (MICs) at temperatures as high as 200°C. The high-temperature contactless probing techniques overcome the limitations of conventional ground-signal-ground coplanar waveguide probes, which rely on good physical contact. They provide a fast, reliable and inexpensive method to quickly screen MICs for high temperature RF telemetry. Novel computational technique is presented to study the terminal influence inside the three-dimensional nano-scale MOSFET PAGE 799 Researchers in Japan present a PLZT capacitor fabrication process with better hydrogen degradation resistance and fatigue endurance by adding a thin aluminium-doped zinc oxide (AZO) buffer layer. This could be applied to ferroelectric random access memory, MEMS and piezoelectric fields. The hydrogen degradation resistance of the PLZT capacitors was improved by over 80% of an initial polarisation value. Contactless radio frequency probes provide a fast, reliable and inexpensive method to quickly screen MICs for high temperature RF telemetry Issue 1 of the IET's latest Letters journal is now available at www.theiet.org/htl with trial access to all content throughout 2014

Experimental results of a direct air-cooled ammonia–lithium nitrate absorption refrigeration system

Absorption thermal cooling systems driven by renewable energy are a viable option in order to reduce fossil fuel consumption and the associated emissions. This work shows the results of an air cooled absorption cooling prototype working with an ammonia–lithium nitrate mixture at high ambient temperatures. An absorption refrigeration system was designed and built. The prototype is a one stage ammonia–lithium nitrate air cooled chiller. The experimental system was instrumented to evaluate each component. This paper shows the operation conditions in the experimental unit as well as some of the heat loads encountered at different operating conditions. The system was operated successfully at ambient temperatures in the range of 25–35 °C. A series of test showed that even at ambient temperatures it can be operated at evaporator temperatures below 10 °C producing chilled water for air conditioning applications such as radiative cooling panels. The system proved to stabilize very quickly and no risk of crystallization was encountered so the first results are promising in order to continue with the development of a more advanced prototype.

Experimental investigation of a novel phase change cold storage used for a solar air-conditioning system

Solar energy systems in combination with thermal driven sorption chillers for air conditioning are gaining increasing attention. Since solar energy is available only during daytime and solar cooling systems are usually intermittent and susceptible to the weather, applying cold storage methods to solar air-conditioning systems is favorable to utilize renewable energy and enhance the system stability. A self-developed phase change material (PCM) providing a suitable phase change temperature of 14.97°C and a reasonable phase transition latent heat of 115.1 kJ/kg is used to fabricate a cold storage tank. The aim of this article is to experimentally investigate the performance of the cold storage tank for solar air-conditioning application. The experiment includes a small-scale steady-state testing of a single spherical capsule and a solar air-conditioning system integrated with the PCM cold storage tank. The temperature distribution and phase change interface movement of the capsule are theoretically predicted. Main parameters of the cold storage tank, namely the inlet and outlet water temperature, internal temperature variation of capsules, charging/discharging capacity and charging/discharging rate are analyzed. The experimental results show that the charging and discharging process completed in 230 min and 220 min under steady states. While under unsteady states of a solar air-conditioning system, the charging and discharging process of the phase change cold storage tank completed within 320 min and 110 min with the total amount of charging and discharging capacity of 1016.1 kJ and 942.8 kJ, respectively. The phase change cold storage tank manifests good feasibility and stability for solar air-conditioning application.

Gas/gas membrane contactors – An emerging membrane unit operation

Gas/gas membrane contactors are devices in which a feed gas and a sweep gas are circulated on either side of a membrane. The pressures of the two gas streams are often approximately equivalent, so the principal driving force for permeation is the concentration difference between the feed and sweep gas components. This type of contactor has been commercialized for energy recovery devices in air conditioning applications. More recently, these contactors have been suggested for use in carbon dioxide capture and sequestration. In this paper, the performance of an ideal contactor using perfectly selective membranes is examined. For this type of ideal contactor, analytical equations can be derived that allow the partial pressure profiles within the contactor to be calculated. The effect of the sweep ratio (sweep flow rate/feed flow rate) and feed pressure on separation performance of the contactors has been calculated. In the final section of the paper, the performance of contactors fitted with membranes permeable to other components of the feed gas is described.

Energy and exergy evaluation of a multiple-PCM thermal storage unit for free cooling applications

Latent heat thermal storage (LHTS) is a technology that can help to reduce energy consumption for cooling applications, where the cold is stored in phase change materials (PCMs). Free cooling is a concept developed for air conditioning applications, in which coolness is collected from ambient air during night and released into the room during the hottest hours of the day. In this work, energy and exergy analyses are performed for a free cooling system using a LHTS unit employing multiple PCMs. The effects of inlet air temperature and air flow rate on the performance of the system are investigated. It is observed that the increase in exergy efficiency due to reducing inlet air temperature is more significant than effect from increasing the air flow rate during the charging process.

Membrane processes for heating, ventilation, and air conditioning

Abstract This article reviews literature on using membranes in heating, ventilation, and air conditioning (HVAC) applications. Membranes enable the separation of one species from another, and membranes allowing the selective permeation of water vapor can be used to condition air in buildings, potentially more efficiently than conventional HVAC equipment. After a brief background on membrane technology, this review focuses on the following processes: vacuum membrane dehumidification; membrane energy recovery ventilation; liquid desiccant dehumidification; liquid desiccant regeneration; evaporative cooling; and humidification. It highlights the design, modeling, and experimental research on these topics, and suggests areas for further research.

A Case Analysis of Application of Evaporative Cooling Air Conditioning of the Communication Equipment Room in Xi’an

Introduced a communication equipment room in Xi'an transition season application tubular I/DEC (Indirect and Direct Evaporative Cooling) projects. The analysis the several modes optimized air handling units throughout the year. Finally, according to the operation of the evaporative cooling air conditioning system in the transitional seasons concluded.

Comparison of the Performance of Single Effect, Half Effect, Double Effect in Series and Inverse Absorption Cooling Systems Operating with the Mixture H2O-LiBr

This paper presents a performance comparison of four different configurations for absorption cooling systems operating with water-lithium bromide mixture. The configurations are: i) single effect, ii) half effect, iii) double effect in series, and iv) double effect inverse. Every system is described in detail and a mathematical model was developed for each one of them. Coefficients of performance and flow ratios are reported for the systems as function of their main operating temperatures, such as: generation, absorption, condensation, and evaporation. From the results analysis regarding to evaporation temperatures, this mixture is easily associated with air-conditioning applications. It is seen that the single effect obtains theoretical coefficients of performance up to 0.89 at generation temperatures between 100°C and 110°C. On the other hand, it was observed that half effect systems may operate with generation temperatures from 55°C, but obtaining coefficients of performance almost half of those obtained with single effect systems. Finally, it was found that double effect systems are the most efficient, reaching coefficients of performance up to 1.48, however, they are more complex and require generation temperatures as high as 158°C. It is important to mention that half effect systems work better than any other when condensation and absorptions temperatures are as high as 40°C.

Numerical Investigation of Internal Pressure in a shell and Tube type of Heat Exchanger by using FEA

Shell and Tube Heat Exchangers are one of the most popular types of exchanger in heat transfer applications. Due to the flexibility, the designer has to allow for a wide range of pressures and temperatures. They are widely used in petroleum refineries, chemical plants, petrochemical plants, natural gas processing, air-conditioning, refrigeration and automotive applications. It utilizes a bundle of tubes through which one of the fluids flows. These tubes are enclosed in a shell with provisions for the other fluid to flow through the spaces between the tubes. In most designs of this type, the free fluid flows roughly perpendicular to the tubes containing the other fluid, in what is known as a cross-flow exchange. In nuclear reactors fuel rods may replace the tubes, and the cooling fluid flowing around the rods removes the heat generated by the fission process.A comprehensive Finite Element Analysis (FEA) has been performed on the critical heat exchanger components in order to validate the results of the components designed using the prescribed codes. The computational analysis helps visualize the areas of high stress concentration thereby aiding the designer to identify the failure prone regions. The regions susceptible to failure can be suitably modified to safeguard against failure. This paper aims at performing a design outputs by IBR codes of critical components of a shell and tube type heat exchanger in an attempt to show the redundancy in designing the components. Furthermore FEA shown the values of stress getting developed in the components for given operating conditions are much lesser than the allowable values of stress for those respective material. Thus the components are safe against such loading.

Measurements and Correlations of cis-1,3,3,3-Tetrafluoroprop-1-ene (R1234ze(Z)) Saturation Pressure

cis-1,3,3,3-Tetrafluoroprop-1-ene (R1234ze(Z)) is being investigated as a working fluid possessing a low global warming potential (GWP) for high-temperature heat pumping applications, organic Rankine cycles, and air-conditioning and refrigeration applications, and as a potential solvent, propellant, and foam blowing agent. Its GWP is less than one. The open literature contains a total of 79 vapor–pressure data from three sources and the critical state properties from a single source. The current paper provides 64 vapor–pressure data from two different laboratories over the temperature range from 238.13 K to 372.61 K. These data are regressed using Wagner and extended Antoine vapor–pressure correlations and then compared to the existing open literature data and correlations. The normal-boiling-point temperature and acentric factor for R1234ze(Z) are estimated to be 282.73 K and 0.3257, respectively.

Optimal Design of a Standalone Photovoltaic Power Supply System for Air Conditioning Application at Samara University as an Alternative to Diesel Generator Source

The aim of this paper is to optimally design a stand alone photovoltaic power supply system for air conditioning application at Samara University to be used as an alternative to diesel generator supply. Samara University is established in samara town, Afar region and has an average daily radiation of 6.10kwh/m2, sun shine duration of about 10 hours. This condition invites the use of photovoltaic system as an alternative primary energy source to replace the existing diesel generator supply system. Therefore in order to use this energy source for air conditioning application, the cooling load of the building, 628 tons, is estimated using Newton’s thumb rule. The evaporative air conditioning system which is sometimes called desert cooler is selected to condition the estimated cooling load of the dwelling room. The sizing method (numerical method and HOMER software tools) is complementarily used to design a standalone photovoltaic power supply system. Finally, the metric value of the present worth is US $ 3,302,066 and its simple payback is 6.6 years, and this foreseen that the attractiveness of photovoltaic power system as one of renewable energy to be used as an alternative to diesel generator in the near future.

Hydrothermal stability of SAPO-34 for refrigeration and air conditioning applications

Hydrothermal stability is one of the crucial factors in applying SAPO-34 molecular sieve to adsorption refrigration. The SAPO-34 was synthesized by a hydrothermal method using diethylamine as a template. Both a vacuum gravimetric method and an intelligent gravimetric analyzer were applied to analyze the water adsorption performance of SAPO-34. Cyclic hydrothermal performance was determined on the modified simulation adsorption refrigeration test rig. Crystal phase, morphology, and porosity of SAPO-34 were characterized by X-ray diffraction, scanning electron microscopy, and N2 sorption, respectively. The results show that, water adsorption strength on SAPO-34 is between that on 13X and A type silica gel. During 100–400Pa, the water uptake on SAPO-34 increases sensitively to pressure, and equilibrium water uptake reaches 0.35kg/kg, 25% higher than 13X. SAPO-34 shows no significant reduced cyclic water uptake over 60 cycles. Most of the initial SAPO-34 phase is restored, while the regular cubic-like morphology is well maintained, and the specific surface area only decreases by 8.6%.

Research on the Application of Green Air Conditioning in the Granary

By describing the environmental requirements for food storage, puts forward the green air conditioning system to create a low-temperature environment for food of these creatures such as ice storage air-conditioning, ground source heat pumps, solar cooling and so on. Combined the related system diagram or schematic in the context of promoting green and healthy, pointed out the future direction of development of the low-temperature grain storage.

Equations of state for HFO-1234ze(E) and their application in the study on refrigeration cycle

This paper aims to describe the thermodynamic properties of the HFO-1234ze(E) with the molecular based BACKONE and PC-SAFT equations of state (EOS) that can be easily extended to mixtures. This paper also evaluates the accuracies of the BACKONE, PC-SAFT, and multi-parameter EOSs. For the data used in the construction of the EOS, the average absolute deviations (AAD) between experimental vapour pressures, experimental saturated liquid densities and values from the BACKONE EOS are 0.34% and 0.42%, respectively. The AAD between experimental vapour pressures, experimental saturated liquid densities and those from the PC-SAFT EOS are 0.16% and 1.51%, respectively. The AAD between predicted compressed liquid densities, predicted isobaric heat capacities, predicted pressures in gaseous phase from the BACKONE EOS and experimental data are 0.60%, 2.29%, and 0.99%, respectively. The AAD between predicted compressed liquid densities, predicted isobaric heat capacities, predicted pressures in gaseous phase from the PC-SAFT EOS and experimental data are 1.35%, 2.91%, and 1.84%, respectively. An independent investigation for data used in the construction of the multi-parameter EOS shows that the AAD between experimental vapour pressures, experimental saturated liquid densities, experimental densities in compressed liquid, experimental isobaric heat capacities, experimental pressures in gaseous phase and those from the multi-parameter EOS are 0.55%, 0.17%, 0.07%, 2.21%, and 0.11%, respectively. The BACKONE, PC-SAFT, and multi-parameter EOSs are used in the investigation of a refrigeration cycle using HFO-1234ze(E) as refrigerant for air-conditioning application. The study shows that the relative differences of all investigated characteristics calculated from thermodynamic properties from these EOSs are mostly within 1%. The thermodynamic properties of HFO-1234ze(E), HFO-1234yf, R-134a, R22, and R32 from the most accurate EOSs are used in the investigation of a refrigeration cycle. The results show that the cycle using R1234ze(E) as refrigerant has the highest coefficient of performance.

Assessment of adsorber bed designs in waste-heat driven adsorption cooling systems for vehicle air conditioning and refrigeration

Abstract Adsorber bed design strongly affects the performance of waste-heat driven adsorption cooling systems (ACS) for vehicle air conditioning and refrigeration (A/C–R) applications. Adsorber beds should be specifically sized for vehicle A/C–R considering the limitations of mobile applications. However, there is no conclusive evidence on what type of adsober bed is proper for vehicle applications. To evaluate the performance of ACS, specific cooling power (SCP), adsorber bed to adsorbent mass ratio, and coefficient of performance (COP) are introduced and their order of importance are assessed. To investigate the available studies in the open literature, desired SCP of 350 W/kg dry adsorbent and adsorber bed to adsorbent mass ratio of less than one are calculated for a 1-ton-of-refrigeration, 2-adsorber bed, silica gel–water ACS. According to these criteria, previous studies are summarized into nine groups with respect to their adsober beds and consequently, finned tube adsorber bed design is selected among the existing designs. Finally, optimization of fin spacing and fin height, and enhancing thermal conductivity of adsorbent material by adding metal wool inside the finned tube adsorber bed are proposed as the practical solutions to increase heat and mass transfer rates within the adsorber bed.