COP Values Research Articles

The Matching Research of Soil Source Heat Pump and Central Heating System in Cold Region

Using Dest software simulation benchmark building the dynamic heat load, analyzing its distribution pattern, at the same timewe can also get heat pump units in the COP value is different under different working condition, then the soil source heat pump and central heating complementary heating system, undertake in soil source heat pump system design heat load, under theconditions of different proportion of the whole system operation energy consumption, initial investment analysis, we conclude thatthe soil source heat pump and central heating complementary heating systems of different energy matching optimization features,this provides a reference for practical engineering.

Energy performance enhancement of Hong Kong International Airport through chilled water system integration and control optimization

Poor energy performances of building systems in practice are often observed, especially under off-design conditions (i.e. at low part load ratios). In order to overcome such problem, most of existing methods are developed merely considering single system or building. Unlike them, a method integrating the chilled water systems in the neighboring buildings is proposed to enhance the overall energy performance of the Hong Kong International Airport. The system integration allows the excessive cooling from one building to be delivered to the other. In addition, one 1000 RT chiller is relocated from Terminal 2 to Terminal 1. After the system integration and chiller relocation, three different sized chillers can be selected to satisfy the overall cooling load with higher part load ratios. Meanwhile, the control optimizations of chillers and seawater pumps also contribute to the system energy performance improvement. With limited investment cost and easy implementation, the proposed method and the control optimization significantly enhance the airport system energy performance. The direct field data comparison demonstrated the average chiller plant COP value is improved by 5.93%. The simulated case studies indicated an annual energy saving about 4.70 M kWh is achievable.

Research of the Refrigeration System of Atmospheric Bridge Type Water Steam Jet Vacuum and Engineering Application

The steam jet vacuum refrigerant device works through the water three state physical change processes, and translates potential energy of low-pressure and low-grade steam into kinetic energy as power source, makes low temperature water above 0°C by water as refrigerant and coolant. The design principle of the device follows the first, the second law of thermodynamics and flow continuous law of hydromechanics, the device adopts installation method of air bridge type, waste heat of steam pressure during 0.05~0.3MPa is source of power,the system adopt 3 effect instead of traditional 2 effect in order to achieve the purpose of energy saving operation, COP value of the refrigerating system is greater than 0.8, refrigerating output of single sets is more than 6000kw. The device is consists of evaporator, the main ejector, the main condenser, auxiliary ejector, auxiliary condenser, water jet and gas-distributing cylinder. And application directions of the type device are studied.

Exergy analysis of single-stage and multi stage thermoelectric cooler

Thermoelectric devices are solid-state devices. Semiconductor thermoelectric cooling, based on the Peltier effect, has interesting capabilities compared to conventional cooling systems. In this work second law analysis of thermoelectric coolers has been done with the help of exergy destruction. In the first part, performance of single-stage thermoelectric coolers and multi stage thermoelectric coolers has been compared for same number of thermoelectric elements i.e. 50. The performance parameters considered to compare their performance are rate of refrigeration, coefficient of performance, second law efficiency and exergy destruction. In second part, multi stage thermoelectric coolers have been analyzed for three different combinations of number of elements in two stages of thermoelectric coolers. The result of the analysis shows that the performance of a multi stage thermoelectric cooler which has total 50 elements gives best performance when it has 30 elements in hotter side and 20 elements in colder side out of the three cases considered. The comparison of single-stage thermoelectric cooler and multistage thermoelectric cooler shows that for same number of elements rate of refrigeration (ROR) of single-stage thermoelectric cooler is much higher than that of multi stage thermoelectric cooler. The COP remains same for both of them but the peak value of cop is obtained at much lower value of current supplied in multi stage thermoelectric cooler. Exergy destruction has constant values in single stage as well as multi stage thermoelectric cooler when the two stages have equal number of elements but it decreases with increase in x. The result of comparison of multistage thermoelectric cooler for three values of x i.e. 0.5, 1, 1.5 shows that the COP, ROR and second law efficiency improve and exergy destruction degrades with increase in x and the best performance has been obtained for x = 1.5 out of the three values considered. Copyright © 2013 John Wiley & Sons, Ltd.

Investigation of the effect of rollbond evaporator design on the performance of direct expansion heat pump experimentally

In this study, the rollbond evaporator design which gives maximum coefficient of performance for the direct expansion solar assisted heat pump (DX-SAHP) water heater is investigated experimentally on the three separate heat pump systems due to the lack of studies on the effect of collector-evaporator design to the system performance. Three DX-SAHP systems are identical except collector-evaporator design. Aluminum is preferred for the evaporator material and R134a as the working fluid.Maximum COP value was obtained as 3.30 for System-1 while COP values for System-2 and System-3 were 3.14 and 2.42 respectively at the same conditions. An empirical correlation which gives the COP value of the System-1, which provides highest COP, with respect to the solar radiation and outdoor temperature of the system has been found using the experimental results obtained during the study. The correlation was found to be in good agreement with the average deviation of 9% with the experimental data.

Communities of practice foster collaboration across public health

PurposeThe complexity and responsibilities of public health make collaboration across multiple levels of government critical. The Centers for Disease Control and Prevention (CDC) effectively uses communities of practice (CoPs) to bring its staff together with partners to share, learn, and address public health problems. This paper aims to focus on CoPs.Design/methodology/approachThe paper assesses the value of CoPs to individual members, their organizations, and their public health domains; assesses whether the CoP Program has improved CDC's relationship with participants in various CoPs; and identifies barriers to participation or success factors that could be applied to the development of new CoPs. Responses from a random sample of active CoP members were analyzed using qualitative data analysis software to identify themes and answer research questions.FindingsThe results reveal clear benefits to individual members, their organizations, and public health disciplines including daily work efficiencies, expanded infrastructure, and enhanced relationships between CDC and its public health partners.Research limitations/implicationsThis qualitative research analyzed a small number of communities of practice spanning their launch through year 2; further study of a larger sample of public health CoPs, including sustainability factors, would build on this case study's implications.Practical implicationsPublic health practitioners seeking a collaborative approach to problem solving will find in this study some useful lessons learned from CDC; readers will be introduced to CDC's CoP Resource Kit and a public health collaboration portal, phConnect.Originality/valueWell‐facilitated, member‐driven, and highly participative CoPs are valuable tools for fostering collaboration essential to improving the public health system, and should be used more broadly across public health.

Experimental investigation on heat recovery from condensation of thermal power plant exhaust steam by a CO2vapor compression cycle

SUMMARY In this paper, a method that utilizes CO2 vapor compression thermodynamic cycle to recover low-temperature heat from exhausted water steam of fossil fuel thermal power plants is reported. Experimental investigation was carried out to study the characteristics of low-temperature heat recovery by liquid CO2 evaporation process from vacuum exhausted steam condensation occurring at the turbine exit. Furthermore, measured heat recovery performances over one whole year are presented and discussed. Experimental results show that the present heat recovery process by CO2 vapor compression cycle is able to operate stably. The yearly averaged water temperature at the CO2 condenser outlet was measured at 87.5 °C with a COP value above 5.0. This high energy efficiency ratio is found to be mainly due to two factors: the transcritical CO2 vapor compression and steam condensation phase change occurring on the CO2 evaporator. The findings from this paper provide helpful guidelines for low-temperature heat recovery system design and improving fossil fuel utilization efficiency. Copyright © 2013 John Wiley & Sons, Ltd.

A comprehensive experimental analysis of gadolinium active magnetic regenerators

The main goal of this study was an experimental comparison of six different active magnetic regenerators (AMRs) with gadolinium as the magnetocaloric material. The analysis was carried out for three different parallel-plate AMRs (with different porosities and different orientations of the plates in the magnetic field) and three different packed-bed AMRs (filled with spheres, powders and cylinders). Since the operation of an AMR is strongly affected by the operating conditions, the experiments were performed at different mass-flow rates and at different operating frequencies. These were required in order to define the optimum corresponding operating conditions for the analyzed AMRs. As comparative criteria the maximum temperature span, the cooling capacity and the experimentally predicted COP were taken into consideration.The experimental analysis was performed on a new prototype of magnetic refrigerator designed as an experimental device. Its operation is based on the linear movement of a permanent-magnet assembly over a static AMR. The magnet assembly provides a measured magnetic field of about 1.15 T.The results reveal that the geometry of the AMR (the form of the magnetocaloric material) has a crucial impact on the performance of the magnetic refrigerator. The best overall cooling characteristics (temperature span, cooling capacity and COP) were obtained for the parallel-plate AMR with the smallest porosity (∼25%) and the orientation of the plates parallel to the magnetic field. This particular AMR generated a temperature span of 20 K, which is also the largest, so-far measured and published temperature span with a parallel-plate AMR for a given magnetic field change generated by permanent magnets. With respect to the comparison of the experimentally predicted COP values, the parallel-plate AMRs show higher efficiencies than the packed-bed AMRs.

Energy and exergy analysis of a solar-assisted heat pump space heating system for clear days

The studies over solar–assisted heat pump systems have been performed mostly on time periods when solar radiation is high. Therefore, this study focuses on performance analysis of a solar–assisted heat pump system which stores the energy during the clear day and uses it as a heat source of heat pump space heating system during the night. Energy and exergy analyses divided into two parts, which are the analyses of solar water heating system (SWHS) and water source heat pump space heating system (WSHPSHS). As a result, the exergy efficiencies of the heat pump unit and WSHPSHS were 84.9% and 79.5%, respectively while the corresponding COP values were 2.95 and 2.68. Also, the exergy efficiency of the SWHS was obtained to be 7.28%. The greatest irreversibility occurs in evaporator, fan–coil unit and solar collector for the heat pump unit, WSHPSHS and SWHS, respectively.

Experimental analysis of R1234yf as a drop-in replacement for R134a in a vapor compression system

This paper presents an experimental analysis of a vapor compression system using R1234yf as a drop-in replacement for R134a. In this work, we compare the energy performance of both refrigerants, R134a and R1234yf, in a monitored vapor compression system under a wide range of working conditions. So, the experimental tests are carried out varying the condensing temperature, the evaporating temperature, the superheating degree, the compressor speed, and the internal heat exchanger use. Comparisons are made taking refrigerant R134a as baseline, and the results show that the cooling capacity obtained with R1234yf in a R134a vapor compression system is about 9% lower than that obtained with R134a in the studied range. Also, when using R1234yf, the system shows values of COP about 19% lower than those obtained using R134a, being the minor difference for higher condensing temperatures. Finally, using an internal heat exchanger these differences in the energy performance are significantly reduced.

Experimental Study on Miniature-Refrigeration System

A prototype of miniature cooling system was developed, which mainly consists of the miniature compressor from DONG YUAN and a spiral-tube evaporator designed by ourselves. The performances of the prototype with different parameters were tested. The influence of ambient temperature, chilled water temperature on the performance of the cooling system were analyzed. The best operating conditions and the optimum amount of refrigerant were obtained. Conclusions were gotten as follows:1) With environment temperature rising, compression ratio increases, system power consumption increases and refrigerating capacity COP decreases. 2) With chilled water temperature rising, compression ratio and power consumption decrease, refrigerating capacity increases, and COP increases rapidly.3) Paper gets system performance: refrigerating capacity is 63 W, compressor power consumption is 24.5 W, COP value is 2.57. in operation condition: refrigerant amount is 40g, environment temperature is 30°C, chilled water temperature is 40 °C, chilled water mass flow is 45 kg/h.

복사패널이 적용된 건물일체형 지열원 시스템의 난방성능 분석

Ground source heat pumps(GSHPs) are among the most efficient and comfortable heating and cooling technologies currently available, because they use the earth`s natural heat to provide heating, cooling, and often, water heating. And Building Integrated Geothermal System(BIGS) is one of GSHPs which install ground heat exchanger(GHE) in energy pile without borehole to save the investment cost. Therefore, the experiment is to evaluate the heating performance of BIGS in Korea. The experimental results indicate that the average heat pump COP and overall system`s COP values are approximately 4.4 and 3.0 in one week. This study shows that the BIGS could be used for heating in Korea.

Enhanced coefficient of performance by effective suction line cooling- an experimental report

The present paper is concerned with theoretical and experimental study and development of effective suction gas heat exchanger for hermetically sealed compressor. A single tube counter flow heat exchanger had been used, where water itself had been taken as a coolant. Energy consumption parameters as well as COP values have been obtained analytically for both the cases. Energy consumption parameter is 12% less as an average for a heat exchanger attached system compared to the system with out heat exchanger in a time span of 90 minutes. COP values obtained with heat exchanger are firmly better than that of the values with out Heat exchanger. COP values observed to be 7% higher for a heat exchanger coupled system compared to the system with out heat exchanger in the same time span of 90 minutes. In the present scenario where systems optimization is a necessity the present work would be useful in developing a energy efficient system with few modifications. This work would be useful to tackle the heat transfer related issues present in many gas compressors used in pumping and process industries.

Experimental Analysis of the By-Pass Air Ratio Effect on the Drying Performance at the Heat Pump Assisted Dryer Systems

In this study, a prototype, closed loop heat pump-assisted dryer (HPD) system with the refrigerant R134a was designed, and tested. The effects of by-pass air ratio (BAR) for two different air flow rates on the system's performance were investigated. The system performances were evaluated in terms of the heat pump performance (COPhp), the performance of all systems (COPsys) and specific moisture extraction rate (SMER). The experimental results showed that bypassing the air more than 50% reduced the COP and SMER values. The COP and SMER values remained nearly constant up to the BAR of 50% and then sharply decreased. The maximum COPhp, COPsys and SMER values were obtained as 4.8, 3.2 and 3.5 kg/kWh, respectively. It was also observed that increasing the air flow rate did not improve the performance of the system. Because, the consumption of the fan was also high, so ITKsis affected negatively.

A Practitioner's Dilemma: How can I calculate the value of communities of practice?

The purpose of this article is to describe a process for evaluating the return on investment (ROI) of communities of practice. Adapting Kirkpatrick's four-step model, Wenger, Trayner and deLaat produced a revolutionary new method for connecting specific CoP activities to organizational results. This article describes the method in order to help practitioners "prove" the value of CoPs to executive-level decision makers.

Effect of Topical Anaesthetics on Interstitial Colloid Osmotic Pressure in Human Subcutaneous Tissue Sampled by Wick Technique

ObjectivesTo measure colloid osmotic pressure in interstitial fluid (COPi) from human subcutaneous tissue with the modified wick technique in order to determine influence of topical application of anaesthetics, dry vs. wet wick and implantation time on COPi.Material and MethodsIn 50 healthy volunteers interstitial fluid (IF) was collected by subcutaneous implantation of multi-filamentous nylon wicks. Study subjects were allocated to two groups; one for comparing COPi obtained from dry and saline soaked wicks, and one for comparing COPi from unanaesthetized skin, and skin after application of a eutectic mixture of local anaesthetic (EMLA®, Astra Zeneca) cream. IF was sampled from the skin of the shoulders, and implantation time was 30, 60, 75, 90 and 120 min. Colloid osmotic pressure was measured with a colloid osmometer. Pain assessment during the procedure was compared for EMLA cream and no topical anaesthesia using a visual analogue scale (VAS) in a subgroup of 10 subjects.ResultsThere were no significant differences between COPi obtained from dry compared to wet wicks, except that the values after 75 and 90 min. were somewhat higher for the dry wicks. Topical anaesthesia with EMLA cream did not affect COPi values. COPi decreased from 30 to 75 min. of implantation (23.2±4.4 mmHg to 19.6±2.9 mmHg, p = 0.008) and subsequently tended to increase until 120 min. EMLA cream resulted in significant lower VAS score for the procedure.ConclusionCOPi from subcutaneous tissue was easily obtained and fluid harvesting was well tolerated when topical anaesthetic was used. The difference in COPi assessed by dry and wet wicks between 75 min. and 90 min. of implantation was in accordance with previous reports. The use of topical analgesia did not influence COPi and topical analgesia may make the wick technique more acceptable for subjects who dislike technical procedures, including children.Trial RegistrationClinicalTrials.gov NCT01044979

Performance of a new two-stage multi-intercooling transcritical CO2 ejector refrigeration cycle

Abstract In this study, a new two-stage multi-intercooling transcritical CO2 refrigeration cycle with ejector-expansion device (MIERC) is investigated. At this studied cycle, the vapor compression line includes two intercoolers, the first with external coolant (air or water) and the second one with cycle refrigerant. The overall performance of the new cycle was compared with that of the conventional ejector refrigeration cycle (CERC) and the internal heat exchanger ejector refrigeration cycle (IHEEC). It was found that the new cycle has the maximum amount of COP and IHEEC has the minimum one. The maximum COP value of the new cycle in the surveyed high-side pressure interval is 15.3% and 19.6% higher than those of CERC and IHEEC respectively. The effect of main cycle parameters such as compressor high-side pressure (discharge pressure), intermediate pressure, gas cooler outlet temperature and evaporator temperature on COP of cycle were studied and results presented here.

Parametric analysis of components effectiveness on desiccant cooling system performance

A number of studies have been conducted for investigating parameters that influence the performance of desiccant cooling systems. Many of these rely on intricate numerical simulations, especially due to coupled non-linear transport equations associated with a desiccant dehumidifier. In this study, a simple numerical procedure for designing desiccant cooling systems has been employed for analyzing the impact of cycle components’ characteristics on the overall system performance. The methodology is based on solving a non-linear algebraic system stemming from heat and mass transfer balances associated with the operation of each component. The required input data involves user-prescribed inlet and room conditions, a regeneration temperature, and cycle components’ effectiveness values. With the proposed methodology, results of different cooling cycles are presented in an informative graphical fashion that can readily be used as a design tool for desiccant cooling systems. The results show that COP values clearly over one can be obtained for ideal ventilation cycles, which have 100% heat wheel effectiveness. Nevertheless, a great reduction, by factors of two and higher, are obtained when this effectiveness is reduced to 0.8. In addition, the results show that a 20–30% decrease in dehumidifier performance can lead to 30–50% reduction in the overall ventilation cycle performance.

Postural Control in Older Patients with Benign Paroxysmal Positional Vertigo

To evaluate the effectiveness of a canalith-repositioning procedure in postural control of older patients with idiopathic benign paroxysmal positional vertigo (BPPV). Prospective clinical trial. A tertiary referral center. A 9-month follow-up survey with a prospective design was conducted among 33 older patients with BPPV. Patients underwent static posturography (Balance Rehabilitation Unit [BRU]) and were administered the Dizziness Handicap Inventory (DHI) before and after the maneuver. After the treatment, they were compared with 33 healthy older subjects. The posturography parameters were the limit of stability (LOS), the center of body-pressure area (COP), and the velocity of oscillation (VOS) under conditions of visual, somatosensory, and visual-vestibular conflict. One canalith-repositioning procedure relieved most patients' complaints (54.5%), and 100% were relieved with 1 to 3 maneuvers. Total DHI score and all subscales improved after treatment (P < .01). The LOS values pretreatment (mean [SD] 134.27 [55.32] cm(2)) and posttreatment (181.03 [47.79] cm(2)) were significantly different (P < .01). Comparative analysis of COP values showed a relevant statistical difference in 8 of 10 postmaneuver conditions (P < .01). The postmaneuver VOS showed a significant difference under 7 conflict conditions. There were no differences between the healthy older subjects and treated patients for all VOS values under all conditions and for COP values under 9 conditions. The canalith-repositioning procedure promotes remission of symptoms, an increase in LOS, and improvement in postural control under conditions of somatosensory and visual conflict and visual-vestibular interaction.

F224 寒冷地対応型植物工場における地中熱源ヒートポンプの評価(OS4 省エネルギー・コジェネ・ヒートポンプ)

Heat pump system is effective in decreasing the fuel costs for heating in the plant factory operation. In the air source heat pump system, the lower the ambient temperature, the lower the efficiency of heat exchange in the evaporator. The low COP value results from the defrosting process in the winter, therefore, the ground source heat pump system is better than the air source heat pump system in the snowy region. The ground temperature is higher than the ambient temperature, and the COP value is higher than that of air source heat pump system. The experience is conducted to evaluate the performance of the ground source heat pump system. The results show that the fuel costs is half of that of the heater using kerosene.