Air Condenser Research Articles

Parameter optimization of passive heat supply tower of ground source heat pump based on NSGA-II

A model that could ensure the lowest energy consumption and optimize all possible performance parameters simultaneously was proposed based on experiments that run the ground source heat pump passive heat supply tower at given conditions. By studying the relationship between the range, approach, tower characteristic ratio, effectiveness, air condensation rate of the passive heat supply tower and water-air ratio, a multi-objective optimization model and its objective function are proposed. With the target of reducing power consumption to the greatest extent, the unconstrained optimization of all objective functions was performed using the Elite Non-dominated Sorting Genetic Algorithm (NSGA-II), in which five performance parameters were adopted to estimate the air flow via decision making at a given water flow rate. The results show that the heat transfer is independent of the water flow. An optimal water-air ratio of 0.48 is determined according to comprehensive analysis of the parameter weights. Under constant water flow rate, the optimal air flow rate and water flow rate is 108.5 g/s and 47.2 g/s, respectively, as observed by comparing the Decision Matrix Score (DMS) value. According to the multi-objective optimization method and the NSGA-II algorithm, optimizations of the performance of supplementary tower are more effective and reasonable as the Decision Making Matrix (DMM) can reasonably allocate parameters expected by users to occupy a larger weight.

Prediction of outlet air temperature of direct air condenser based on BP neural network

At present, the dynamic parameter monitoring technology of the direct air cooling system is relatively weak. According to the study of outlet air flow temperature characteristics, this paper proposes a direct air condensing unit outlet air flow temperature prediction model based on BP neural network for studying dynamic parameters of direct air cooling units. The historical data of each factor is collected from the on-site DCS system. After the data is preprocessed, the BP neural network is used to establish the air temperature prediction model of the air condenser. Finally, the model is validated by the data that does not participate in the training. The model can predict the outlet air temperature of the air condenser under different working conditions, providing a basis for the next step of developing dynamic parameter monitoring technology, and also provide a reference for the cleaning cycle of the air condenser.

Exergy Analysis of Electric Vehicle Heat Pump Air Conditioning System with Battery Thermal Management System

The exergy analysis of an electric vehicle heat pump air conditioning system (HPACS) with battery thermal management system was carried out by studying the exergy loss of each component. The results indicate that the compressor is the main source of system exergy loss in all operation conditions. The exergy loss distribution of HPACS is almost the same when the battery thermal management system integrated into the HPACS in cabin and battery mixed cooling mode and the system exergy loss was linearly related to the compressor speed in cooling modes. The performance of the HPACS is better than that of the positive temperature coefficient (PTC) heater in cabin heating mode. The degree of exergy efficiency improvement of the alternative mode was discussed at all operation conditions in cabin heating mode. The results indicate that the optimization effect using the electric vehicle HPACS to replace the PTC heater is obvious at lower compressor speed, surrounding temperature and internal condenser air flow rate.

A sampler prototype for the simultaneous collection of exhaled air and breath condensate.

Exhaled air and breath condensate contain a large number of health biomarkers, such as volatile and semi-volatile organic compounds, proteins and lipids. Nowadays, the collection of breath samples is carried out by commercial or lab-made sampling systems that collect only one type of sample (e.g. gaseous or condensate phase), thus limiting the diagnostic capability of breath tests. This work presents a portable prototype optimized for the simultaneous collection of gaseous exhaled breath and exhaled breath condensate within five minutes. The system is fully portable and has a total weight of about 1 Kg. An illustrative determination of ethanol, isoprene, acetone, isopropyl alcohol, 1-propanol, 2-butanone, 2-pentanone, toluene and xylenes in breath, and cortisol and 8-iso-prostaglandin F2α in breath condensate is discussed.

Electrowetting-based enhancement of droplet growth dynamics and heat transfer during humid air condensation

Condensation heat transfer can be significantly enhanced by condensing vapor as droplets (instead of a film), which rapidly roll-off. This work studies the use of electrowetting to enhance coalescence, growth and roll-off dynamics of condensed droplets, thereby enhancing the condensation rate and associated heat transfer. This enhancement depends on the nature of fluid motion (translation of droplets, oscillations of the three phase line), which in turn depends on the magnitude and frequency of the applied electrical actuation waveform. Experiments are conducted to study early-stage droplet growth dynamics, as well as steady state condensation under the influence of an electric field. It is seen that droplet growth is enhanced as the voltage and frequency of AC electric fields is increased, with AC electric fields seen to be more effective than DC electric fields. Roll-off dynamics also depends on the frequency of the AC field. Overall, electric fields alter the droplet size distribution and move the condensate to more favorable states for removal from the surface. The condensation rate depends on the roll-off diameter of the droplet, frequency of roll-off events, and on the interactions of the rolled-off droplets with the remainder of the droplets. An analytical heat transfer model is utilized to relate the measured condensation rate with condensation heat transfer. It is noted that this study deals with condensation of humid air, and not pure steam. Overall, this study reports more than 30% enhancement in condensation rate resulting from the applied electric field, which highlights the attractiveness of electrowetting for condensation heat transfer enhancement.

Experiments for suitability of plastic heat exchangers for dehumidification applications

The present study conducted a series of experiments concerning the condensation of humid air used in a typical adsorption dehumidifier. The experiments were carried out with the standard ambient condition (27 °C dry bulb temperature and 21.2 °C wet bulb temperature) for the cold side. Yet the regeneration side (hot side) inlet temperature is 55 °C with RH% being 100%. Three novel plastic heat exchangers (plate plastic heat exchanger-PHX, bare tube plastic heat exchanger with asymmetry tube layout-BTHX, and round tube plastic heat exchanger with uniform tube layout-RTHX) were tested and compared experimentally. Test results, in terms of heat flux or heat transfer coefficient, show that the BTHX is superior to RTHX and PHX for offering additional condensate splashing mode. The splashing feature is especially beneficial for larger cold side flow rate since the plateau of heat transfer performance is moved toward larger cold side flow rate regime. The asymmetry tube geometry design (BTHX) shows even better heat transfer performance than the uniform tube bundle design (RTHX) for providing more space at the downstream of the tube bundle.

ПАРАМЕТРИЧЕСКИЙ АНАЛИЗ СХЕМЫ ПАРОГАЗОВОЙ УСТАНОВКИ С КОМБИНАЦИЕЙ ТРЕХ ЦИКЛОВ ДЛЯ ПОВЫШЕНИЯ КПД ПРИ РАБОТЕ В СЕВЕРНЫХ ГАЗОДОБЫВАЮЩИХ РАЙОНАХ

Актуальность. Парогазовые установки рассматриваются как одно из перспективных направлений развития теплоэнергетических установок, работающих на природном газе. Интерес к их внедрению в России объясняется большими запасами природного газа, низкими капиталовложениями и минимальными выбросами вредных веществ в окружающую среду. Из термодинамики известно, что для достижения высокого КПД цикла необходимо иметь высокую температуру подвода теплоты и низкую температуру ее отвода, а также обеспечить работу оборудования с минимальными внутренними потерями и иметь рациональную тепловую схему взаимосвязи оборудования в цикле. На современном этапе максимальная температура подвода теплоты в камере сгорания газотурбинной установки при существующих конструкционных материалах и способах охлаждения элементов турбины достигла 1600 °С, а температура отвода теплоты в конденсаторе при работе цикла Ренкина на воде по условиям экономичности не может быть ниже 15 °С. При этих условиях на наиболее совершенных трехконтурных парогазовых установках с промежуточным перегревом пара достигнут электрический КПД 63 %. Для цикла Ренкина при работе на воде температура конденсации пара по условию замерзания должна быть выше 0 °С. Для парогазовой установки при работе в условиях низких среднегодовых температур окружающей среды, что характерно для России и особенно отдаленных северных районов добычи газа, можно отводить теплоту в цикле Ренкина значительно ниже 0 °С, но это надежно можно выполнить только применяя конденсаторы с воздушным охлаждением, если в качестве рабочего тела в цикле Ренкина использовать органическое рабочее тело. Недостатком современных органических рабочих тел является низкая предельная температура их термического разложения, которая составляет 300…400 °С. Объект: парогазовые установки с циклами на трех рабочих телах, где верхний цикл Брайтона работает на продуктах сгорания природного газа, средний – цикл Ренкина – работает на воде и водяном паре в интервале температур 100…650 °С, а нижний – Органический цикл Ренкина – работает на органических рабочих телах в интервале температур –30…250 °С. Цель: выбор рациональной технологической схемы парогазовой установки c применением циклов на трех рабочих телах и воздушного конденсатора для возможности надежного отвода теплоты от органического рабочего тела при температуре ниже 0 °С и определение оптимальных параметров циклов. Методы. Сложные теплоэнергетические системы, включая парогазовые установки, характеризуются многообразием процессов, протекающих в их элементах. Такие установки можно эффективно исследовать только с помощью методов математического моделирования и оптимизации. При проведении исследований в данной работе использован системный подход, методы энергетических балансов и расчет термодинамических и теплофизических параметров рабочих тел с помощью современных сертифицированных программ. Результаты. Разработана оригинальная схема парогазовой установки утилизационного типа с циклами на трех рабочих телах, где верхний цикл Брайтона работает на продуктах сгорания природного газа, средний цикл Ренкина работает на воде и водяном паре, нижний – Органический цикл Ренкина – работает на органическом рабочем теле с конденсацией его в воздушном конденсаторе. Разработана математическая модель и программа расчета предложенной схемы. Определено наиболее эффективное органическое рабочее тело для нижнего цикла Ренкина. Проведен параметрический анализ влияния основных параметров циклов на КПД брутто и нетто парогазовой установки.

Fatigue and Corrosion Fatigue Behaviour of Brazed Stainless Steel Joints AISI 304L/BAu-4 in Synthetic Exhaust Gas Condensate.

As brazed stainless steel components in service often have to withstand cyclic loads in corrosive environments, the corrosion fatigue properties of brazed joints have to be characterised. Application-relevant corrosion fatigue tests in corrosive media are extremely rare for brazed joints and cyclic deformation curves are barely investigated. In this study, fatigue tests of brazed AISI 304L/BAu-4 joints were performed in air and synthetic exhaust gas condensate K2.2 according to VDA 230-214. The fatigue behaviour of the brazed joints was compared to properties of the austenitic base material. Strain, electrical, magnetic, temperature and electrochemical measurement techniques were applied within fatigue and corrosion fatigue tests to characterise the cyclic deformation and damage behaviour of the brazed joints. It was found that the fatigue strength of 397 MPa at 2 × 106 cycles was reduced down to 51% due to the superimposed corrosive loading. Divergent microstructure-related damage mechanisms were identified for corrosion fatigue loadings and fatigue loadings of specimens in the as-received and pre-corroded conditions. The investigations demonstrate the important role of corrosive environments for the mechanical performance of brazed stainless steel joints.

Numerical analysis of factors affecting condensation capacity of air-cooled condenser

The working environment of the air-cooled condenser is very complicated. By analyzing the heat transfer process of the air-cooled condenser, it is found that the temperature of the environment, the lateral wind speed in the environment and the rotational speed of the axial fan all have an influence on the condensation capacity of the air-cooled condenser. Through research, it is found that the condensation capacity of the space-time condenser at -25 ° C is about 3.75 times that at 30 ° C; compared with no lateral wind speed, when the wind speed increases from 4m/s to 12m/s, the decline of the condensation capacity of the air condenser changes from 1.2% to 12.6%; when the axial fan is at 1.1 times rated speed, its condensation capacity is 1.6 times that of 0.5 times. It can be seen that the rotational speed of the axial flow fan and the ambient temperature are the main influencing factors, and the rotational speed of the axial flow fan is an active adjustment factor. Furthermore, the control scheme of the axial fan speed as a function of ambient temperature can be obtained through analysis.

Performance prediction of finned air-cooled condenser using a conjugate heat-transfer model

Finned air-cooling condensers save a significant amount of water in Rankine cycle power plants; however, their heat-removal capability is difficult to predict due to the condensation in finned tubes resulting from the coupled heat transfer between vapor and cooling air fluid. This study develops a conjugate-model-based approach to characterize the thermal-hydraulic development by the transverse flow of vapor and cooling air in a finned tube, and to quantify effects of varying vapor and cooling air operation on the in-tube condensation and out-tube air convection. The approach proposes all uncoupled conditions of a conjugate model on the heat-exchange interfaces, which guarantees that the temperature and heat flux are equal everywhere on the finned tube. Applied to an engineering finned tube, the model verifies that a high vapor mass flux likely reduces the condensation level, and the effect of non-condensable gases with the inlet mass fraction of 0–5% is negligible to the vapor condensation; an increase of cooling air velocity enhances the performance of both vapor condensation and cooling air convection effectively, and a decrease of atmosphere pressure reduces them obviously. The approach is beneficial in designing an enhanced finned tube and operating a field condenser efficiently.

The interaction effects between droplets condensing from moist air using a distributed point sink method

In modelling dropwise condensation, growth of the droplet is frequently assumed in an isolated form. However, for dropwise condensation of moist air the vapor diffusion from the surrounding to the droplet surface will be tremendously influenced by the blocking effect of the neighboring droplets. The influenced spatial distribution of water vapor totally determines a different condensation rate comparing with that by the isolated droplet model. In this work, a distributed point method (DPSM) as the methodof Green function is developed to capture the interaction effects of droplets without requiring solution of the diffusion equation and the numerical discretization. Due to its nature, the automaticallysatisfied boundary conditions make sure the solution accuracy based on the uniqueness theorem. The significant characteristics for the interaction effects between droplets are investigated by handling a series of droplet arrays. During dropwise condensation, a typical droplet array containing up to 1000 droplets is considered. The results indicate that the interaction effect between droplets is critical in accurately predicting the condensation behavior for dropwise condensation in the presence of non-condensable gas.

Analysis on the Calculating of Air Leakage Threshold which Caused the Condenser Vacuum Deterioration

There is an air leakage threshold under certain condenser heat load and air ejector output. When the amount of air leakage is less than the threshold, the condenser pressure is essentially the same, we can maintain a stable condenser vacuum, once exceed the threshold, condenser pressure begin to gradually larger, condenser vacuum will deteriorate. Considered the air leakage influences on the heat transfer coefficient of condenser, this paper had been established the one-dimensional steady-state heat transfer model of condenser to obtain the condenser pressure curve along with the amount of air leakage, the turning point on the curve is the air leakage threshold.

Experimental study of pure steam and steam–air condensation over a vertical corrugated tube

The natural convection condensation heat transfer outside the vertical smooth tube and corrugated tube was experimentally investigated in pure steam and steam–air conditions, respectively. The aim of the research was to evaluate the heat removal capacity of the corrugated tube through comparing with the test results of the smooth tube. In the experiment, a corrugated tube was tested, the bulk temperature and the wall temperature of crest and trough were measured in detail. The result of the temperature measurement demonstrated that the difference of heat transfer characteristics at the crest and trough is not significant. In the pure steam condition, the influence of subcooling on condensation heat transfer coefficient of the corrugated tube is reduced. Comparing with the smooth tube, the condensation heat transfer coefficient of the corrugated tube has been increased for more than 10%. In the steam–air test condition, the condensation heat transfer coefficients have been obtained for the air mass fraction from 0.1 to 0.95 and the total pressure from 0.2 MPa to 0.5 MPa. The corrugated tube shows a slight enhancement with an average increase of condensing heat transfer coefficient about 10%.

Frequency‐dependent fatigue and corrosion fatigue assessment of brazed AISI 304L/BNi‐2 joints in air and synthetic exhaust gas condensate

AbstractSince brazed components are often cyclically loaded in corrosive environments, the corrosion fatigue behaviour of the joints has to be investigated. Fatigue tests of brazed AISI 304L/BNi‐2 joints, relevant for exhaust gas heat exchangers, were performed with specimens in the as‐received condition and after pre‐corrosion according to VDA 230‐214. Additionally, the superimposed corrosion fatigue loading in an exhaust gas condensate was realised using a corrosion cell. Corrosion‐induced and deformation‐induced microstructural changes were metallographically evaluated. The influence of the test frequency from 1 to 150 Hz on the cyclic deformation and damage behaviour was characterised. In a statistical analysis, the fatigue strength of 210 MPa at 2·107 cycles was determined for the as‐received condition with a 50% failure probability. The pre‐corrosion as well as the superimposed loading lead to a reduction of the fatigue strength down to 22%. A novel test strategy is suitable for precise fatigue and corrosion fatigue assessments.

Energy and water recovery using air-handling unit condensate from laboratory HVAC systems

This paper examines ways to reduce energy and water consumption in laboratory HVAC systems. The data add to existing research into reduced potable water consumption derived from air handling unit (AHU) condensate. It also explores and validates the potential for energy recovery.The literature shows that hot, humid climates can be ideal for AHU condensate to be leveraged as a source for pre-cooling and dehumidifying. The findings also reveal locations best suited for its application, because condensate generation is greatest when pre-cooling and dehumidification are needed most. Psychrometric relationships are used to predict condensate generation based upon ambient meteorological conditions.Since laboratories require high volumes of 100% outside air, data show they are the perfect candidates to re-use relatively pure, cold condensate. This study analyzes AHU condensate utilization for both energy and water recovery modes; evaporative pre-cooling for sensible energy recovery, and condensate as a source for cooling tower make-up water. An optimization scheme is presented that maximizes energy and water savings based on outside air enthalpy, condensation generation, and energy recovery mode.

Effects of humid air on aerodynamic journal bearings

Abstract The development of aerodynamic bearings applications where ambient conditions cannot be controlled (e.g., for automotive fuel cell compressor) raises the question of the effects of condensation in the humid air on performance. A modified Reynolds equation is obtained in relation to humid air thermodynamic equations, accounting for the variation of compressibility and viscosity in the gas mixture. The load capacity and stability of plain and herringbone-grooved journal bearings is computed on a wide range of operating and ambient conditions. In general, performance metrics show an independence on humid-air effects at moderated temperature, although the stability of the grooved journal bearing exhibits strong variations in particular conditions. In consequence, a safety margin of 25% is suggested for the critical mass.

Experimental performance study of R290 as an alternative to R22 refrigerant in a window air conditioner

R22 is a hydrochloroflurocarbon (HCFC) refrigerant widely used in air conditioning. R22 is an ozone depleting substance. Due to ozone layer depletion, HCFC will be phased out in near future. R290 is hydrocarbon (HC) refrigerant is an alternative to R22. This paper presents outcomes of this comparative study. A 1 ton capacity window air conditioner was used to experiment. R22 was used for baseline refrigerant. R290 refrigerant using air cooled condenser coefficient of performance (C.O.P.) lowered by 6.91%, 6.28% & 1.38% at different set point temperatures 16°C, 20°C& 25°C. The system is optimized to increase in thermodynamic performance by using evaporative cooling condenser with R290 refrigerant. C.O.P. of system is improved by 15.84%, 18.23% & 22.92% at different set point temperature and power consumption reduces by almost 50% than the baseline system. The amount of refrigerant charge of R290 refrigerant is 70% less than that of R22 refrigerant. Experimental results show that implementation of the evaporative cooled air condenser by using R290 refrigerant has a significant effect on performance improvement of window air conditioner.

Experimental Investigations on the Performance Enhancement Using Minichannel Evaporator with Integrated Receiver-Dryer Condenser in an Automotive Air Conditioning System

ABSTRACTThe performance comparison of two automotive air conditioning systems was experimentally studied under two typical cabin conditions viz; 27°C dry bulb temperature / 40% relative humidity and 40°C dry bulb temperature /40% relative humidity in a bench test rig for different blower speeds of the evaporator. Two mobile air conditioning systems viz; enhanced system having minichannel evaporator with integrated receiver-dryer condenser, and baseline system having conventional serpentine evaporator with parallel flow condenser were considered for the study. The compressor was the same for both the systems. The charge quantity, compressor speed, condenser air flow rate were suitably modified to maintain similar suction / discharge pressures, suction super heat and sub-cooling at all test conditions. The percentage of condensate retention during the dehumidification for both the evaporators were also compared. The comparison indicates that the average coefficient of performance of the enhanced system is higher in both low and high cabin temperature condition by about 15% and 8% respectively. The percentage of condensate retention in the evaporator of the enhanced system is lesser in the range of about 17–31% as compared to the base line system evaporator. It is also expected that a specific design of compressor for the enhanced system can yield better performance at all conditions.

Assessing the airtightness performance of container houses in relation to its effect on energy efficiency

This study examines the airtightness performance of four types of commonly-used container houses (CHs) and its impact on their energy efficiency. One of the CHs was treated by sealing all junctions inside the container envelope. The airtightness levels of unsealed and sealed CHs were measured by using the fan pressurization method. The interior surfaces of building envelope were scanned by thermal imaging in order to locate the areas suffering from air leakages and thermal failures. The annual energy consumptions of unsealed and sealed CHs for their heating were predicted by energy simulation analyses. The unsealed CHs have poor airtightness features while performing in Energy Rating B category. The junctions of those houses, especially where wall, slab and roof panels come together and the edges of the openings also suffer from air leakages, thermal bridges and condensation. Sealing the interior surfaces of junctions and edges improves the airtightness level considerably while heat loss and condensation problems at the junctions still continue. An 81% improvement in airtightness performance of the CH Type B provided a reduction of 9.3% in annual energy demand which is not enough to step up its Energy Rating category. The results indicate that airtight jointing is needed at junctions while the use of thermal breaks at junction details has vital importance to eliminate thermal failures and to improve energy efficiency performance of CHs. The combined use of Blower Test Method and Infrared Thermography is useful for non-destructive assessment of airtightness features of building envelopes.

Proteomic characterization of human exhaled breath condensate

To improve biomedical knowledge and to support biomarker discovery studies, it is essential to establish comprehensive proteome maps for human tissues and biofluids, and to make them publicly accessible. In this study, we performed an in-depth proteomics characterization of exhaled breath condensate (EBC), a sample obtained non-invasively by condensation of exhaled air that contains submicron droplets of airway lining fluid. Two pooled samples of EBC, each obtained from 10 healthy donors, were processed using a straightforward protocol based on sample lyophilization, in-gel digestion and liquid chromatography tandem-mass spectrometry analysis. Two ‘technical’ control samples were processed in parallel to the pooled samples to correct for exogenous protein contamination. A total of 229 unique proteins were identified in EBC among which 153 proteins were detected in both EBC pooled samples. A detailed bioinformatics analysis of these 153 proteins showed that most of the proteins identified corresponded to proteins secreted in the respiratory tract (lung, bronchi). Eight proteins were salivary proteins. Our dataset is described and has been made accessible through the ProteomeXchange database (dataset identifier: PXD007591) and is expected to be useful for future MS-based biomarker studies using EBC as the diagnostic specimen.