A new system solution has been developed and tested by the authors and has been shown to improve the Seasonal Energy Efficiency Rating (SEER) of fixed-speed condenser split-system residential heat pumps. This is achieved through the use of a low power electronic drive that allows components with PSC motors (such as fans and compressors) to operate at multiple low speeds or variable speeds when partial capacity is required. At full capacity, the electronic drive is disabled and the PSC motors are operated at fixed speeds dictated by the frequency of the power source. Previous research by the authors has shown that fixed-speed heat pumps driven by rotary compressors with PSC motors achieve significantly greater improvements in performance and in overall SEER when operated with the electronic drive than similar heat pumps driven by scroll compressors with PSC motors. The current research measures the compressor and drive performance through calorimeter testing. This paper presents the results of testing a dual rotary PSC compressor in variable speed mode in association with the new electronic drive. The purpose of this testing is to understand how an off-the-shelf compressor with a PSC motor intended for fixed-speed operation performs under variable speed operation. Preliminary results of testing a PSC scroll compressor in variable speed mode with the electronic drive are also presented for comparison with the rotary compressor. Future research will focus on testing other common HVAC compressor technologies and employing mechanistic compressor models in order to better understand the parameters which affect the performance of PSC driven compressors under variable speed operation.

A new type of thin-walled steel tube/bamboo plywood hollow composite column with binding bars (SBCCB) that used transverse binding bars to reinforce the composite column was developed. The compression performance of 4 specimens with larger slenderness ratio was tested to examine the failure mode of the SBCCBs. The results indicated that the compression failure modes are mainly crushing failure of the bamboo plywood material, partial debonding failure of the adhesion interface and buckling instability failure; the ultimate bearing capacity of the specimens is not only related to net cross-sectional area and slenderness ratio, but also greatly affected due to binding bars. Transverse binding bars can ensure the integrity of the composite column, effectively reduce the debonding failure of the adhesion interface and significantly improve the load-bearing capacity of the SBCCBs.

A comprehensive simulation model is presented to predict the performance of a hermetic reciprocating compressor and to reveal the underlying mechanisms when the compressor is running. The presented model is composed of sub-models simulating the in-cylinder compression process, piston ring/journal bearing frictional power loss, single phase induction motor and the overall compressor energy balance among different compressor components. The valve model, leakage through piston ring model and in-cylinder heat transfer model are also incorporated into the in-cylinder compression process model. A numerical algorithm solving the model is introduced. The predicted results of the compressor mass flow rate and input power consumption are compared to the published compressor map values. Future work will focus on detailed experimental validation of the model and parametric studies investigating the effects of structural parameters, including the stroke-to-bore ratio, on the compressor performance.

A mobile carbon dioxide (CO2) refrigeration system is investigated to simultaneously provide a multi-temperature refrigerated container system (MTRCS) with the required cooling capacities. A two-evaporator system combined with multiple compression stages is considered. The high temperature (H.T.) evaporator is used to cool two-thirds of the container to 38 degrees F (3. 33 degrees C), while the low temperature (L.T.) evaporator cools the remaining one-third of the container to -5 degrees F (-20. 56 degrees C). Four possible cycle configurations are investigated and compared with each other. It is found that the cycle which employs a 3-stage compression concept incorporated with intercooling and flash tank economizing technology can achieve the best system performance and lowest discharge temperature. Moreover, an expander is used in this cycle to replace the expansion valve between the high-side pressure and intermediate pressure to recover the work loss during the expansion process leading to an even better system performance.

A simulation model to predict the performance of a prototype CO, compressor is presented. This prototvpc compressor employs the Sanderson-Rocker Arm Motion (S-RAM) mechanism, which converts the rotary motion of the shaft into a linear reciprocating motion of the cylinders. The piston stroke can be variable by changing the incline angle between the connecting rod and compressor main shaft centerline. The compressor model is mainly composed of two main sub-models simulating the kinematics of the drive mechanism and the compression process. A valve sub-model is included in the compression process model.

Existing modeling approaches for passive chilled beams are not adequate for assessing overall energy usage and occupant comfort within building simulation programs. In addition, design guidelines for passive chilled beam systems are needed for identifying appropriate applications and optimal configurations. This work will develop improved passive chilled beam testing approaches and semi-empirical modeling that will allow performance measurements from tests on a single chilled beam in a laboratory setting to be used in modeling multiple chilled beams in a building application within a building simulation tool. The research includes characterizing the performance of passive chilled beams by experimental investigations and development of models, and integration of these models into building simulation models for overall assessments of passive chilled beam systems. The integrated simulation tool will be used to perform comprehensive comparisons of passive chilled beam and conventional systems in order to provide guidelines for appropriate applications. A single passive chilled beam is being tested under controlled conditions to acquire measurements that can be further used to develop a semi-empirical model. Comprehensive measurement parameters are considered to capture both convection and radiation cooling capabilities of the passive chilled beam. The performance of passive chilled beams is relatively more affected by the indoor conditions compared to conventional cooling systems due to the naturally convective cooling nature. For this reason, field measurements from a real occupied office space installed with multiple passive chilled beams are also taken to verify the validity of using the model developed from laboratory tests on a single passive chilled beam in a system simulation for spaces with multiple chilled beams. The most cost-effective and precise method of estimating the annual performance of radiant heating and cooling systems (including passive chilled beam system) in terms of energy efficiency and thermal comfort is to use a dynamic building simulation tool due to the mix of convective and radiative heat transfer characteristics. Thus, an integrated building simulation model is chosen and is being developed in this study to assess and optimize the passive chilled beam at a system level and to compare it with conventional cooling systems. The computationally efficient semi-empirical passive chilled beam model that will be developed based on experiments will be implemented in the integrated building simulation model. This integrated building simulation model will be used to evaluate overall energy usage of chilled beam systems compared to conventional cooling systems and other passive ceiling cooling systems under different simulated weather conditions. Optimizing design and operation of the passive chilled beam system will also be performed with this integrated model in terms of sizing, control and installation layout, which will help for the penetration into the market.

Approaching quasi-isothermal compression is possible by flooding the refrigerant vapor stream with a liquid that has high specific heat to absorb some heat of compression. To evaluate the benefits of liquid flooded compression, an R410A scroll compressor was tested over a wide range of operating conditions while flooding POE oil into the compression chamber using a hot-gas bypass test stand. The experimental results indicate that oil flooded compression leads to an increase in refrigerant mass flow rate and a decrease in compressor discharge temperature. Also, every operating condition has a maximum limit of possible oil injection, which depends on the system pressure ratio and the dimensions of the injection and discharge ports. By fitting the experimental data, a performance map for the compressor with oil flooding is developed using a semi-empirical model. This map can be used to assess the benefits of the oil flooding technology for various conditions employed in other applications.

为了研究闭式循环柴油机中超重力旋转床的水吸收二氧化碳过程,开展了仿真与实验研究.建立旋转床三维物理模型,采用欧拉-拉格朗日两相流模型对气液流场进行流体力学计算.以希格比的溶质渗透理论为基础,设置气相源项,对液相吸收二氧化碳过程进行仿真.并通过实验验证不同操作参数对其吸收性能的影响.结果表明:吸收过程在靠近丝网与分布器位置较为强烈,吸收性能随着旋转床转速与吸收因数增加而加强,随着进气浓度增加而降低.仿真中设置的源项能模拟床内吸收的过程,仿真与实验得出的液相传质单元数有较高的一致性,平均相对误差在10％左右,最大误差为20.6％,在高进气浓度下仿真偏差较大.总的来说,仿真能较好地模拟实际二氧化碳在旋转床中的吸收过程.

In this paper, a prototype positive-displacement oil-free carbon dioxide (CO2) compressor with a novel mechanical linkage system is introduced and tested. Preliminary compressor test results of the volumetric efficiency and overall isentropic efficiency are presented. The novel compressor design introduces a new low-friction, variabledisplacement drive mechanism. The displacement of the compressor can be varied mechanically while maintaining a minor constant head clearance, eliminating the need for variable speed motors and variable frequency drives. The compressor was designed and manufactured to provide cooling capacities from 10 kW to 100 kW by changing the displacement of the piston. A test stand was constructed to map the compressor isentropic efficiency, volumetric efficiency, mass flow rate, power consumption and discharge temperature. The test stand is based on a hot gas bypass design, in which a part of the discharged refrigerant flow bypasses the condenser, whereas the other part of the flow changes phase as it flows through the condenser. The two streams are mixed to obtain the desired compressor superheat at the suction side of the compressor. The bypass valve enables control of the suction pressure as the discharge valve controls the discharge pressure. The prototype compressor was tested at pressure ratios (PR) of 1.5, 2, 2.5, and 3 at 25 Hz (≈750 rpm), and additionally at PRs of 1.5, 2, and 3 at 20 Hz (≈600 rpm). Based on the test results, the maximum isentropic efficiency is 76% at 20 Hz (592 rpm) and a PR of 2, while the volumetric efficiency is 88%.

The heating capacity and coefficient of performance (COP) of conventional air-source heat pumps decreases towards lower ambient temperatures. In addition, high discharge temperature at the compressor discharge might limit the operation of the heat pump at very low ambient temperatures. Oil injected into the compression chamber at the beginning of the compression process can absorb part of the heat generated during the compression process, which can result in significant reduction of the compressor discharge temperature. Discharge temperature decreases with increasing injected oil mass fraction, especially at low ambient temperatures. Therefore, oil injection allows the application of air-source heat pumps in regions with very low ambient temperatures in winter. Additionally, oil injection decreases the compressor power consumption by providing better sealing and lower friction during the compression process. Furthermore, if oil injection is combined with a regenerative heat exchanger and an oil cooler, the system performance of a vapor compression system can be improved significantly. The work presented in this paper shows the experimental results of a 5-ton (17.6 kW) R410A packaged heat pump which was retrofitted with an oil injected compressor, integrated indoor heat exchanger oil cooler and regenerator. The effect of different oil mass fractions on the system performance was investigated under standard AHRI 210/240 heating test conditions. According to the results, up to 8% system COP improvement was observed compared to the baseline system for all ambient temperatures.

Previous research indicates that a scroll compresso r with multiple vapor injection ports has the poten tial to significantly improve the energy efficiency and hea ting capacity of vapor compression heat pumps, part icularly at low outdoor temperatures. Based on a tradeoff betwe en cost and benefit, a dual-port vapor injected com pressor prototype was chosen for testing to provide experim ental validation of the efficiency benefits. The ov erall performance of a heat pump system employing the compressor prototype was analyzed. Coupling the compressor testing results with a three-stage expansion vapor injection flash tank cycle model, the operating inj ection pressures were determined for different working conditions. T he results showed that injection pressures and corr esponding injected mass flow rates decreased with an increase of ratio of discharge to suction pressure. Compari ng the COP of the vapor injection cycle with a baseline cycle, th e improvement in COP increased with an increase of the pressure ratio and was 19% for cold climate heating conditio ns with an evaporating temperature of -30°C and a c ondensing temperature of 43.3°C.

A comprehensive model for a semi-hermetic CO2 reciprocating compressor is presented. This comprehensive model is composed of three main sub-models simulating the geometry and kinematics, the compression process, and frictional power loss. Valve and leakage sub-models are included in the compression process model. The frictional power loss model includes the friction at the bearings and between the piston ring and cylinder wall. The predicted results of the comprehensive model are validated using external compressor performance measurements of compressor input power and mass flow rate. The mass flow rate and compressor input power are predicted to within 4.03% and 6.43% mean absolute error, respectively, compared to the experimental datum. Additionally, a parametric study is presented which investigates compressor performance as a function of the stroke-to-bore ratio.

A theoretical model of carbon dioxide solubility in alkyl naphthalene oil was established with the modified state equation on the basis of the molecular aggregation theory and the corresponding mixing rules. The critical physical properties of the oil were determined by the group contribution method. The comparison shows that the predictions of the carbon dioxide solubility in alkyl naphthalene oil by the solubility model based on the modified vdWaals equation agree well with the existing experimental data with a mean error of 5. 56% and 3. 47% under the experimental conditions, respectively. Moreover, the more precise value can be obtained at the higher carbon dioxide solubility because of the more obvious molecular aggregation phenomenon. However, the large errors of 48.92% and 46.91% confirm that the modified PR and RKS equations may not be applicable to determining the solubility of carbon dioxide in alkyl naphthalene oil. In addition, the variation of the solubility was predicted using the model developed. The results show that the solubility increases by about 19% from 3. 5 MPa to 4. 5 MPa at 0°C and 10°C, and decreases by 20. 9% and 12. 5%, respectively, when the superheat temperature is from 0°C to 20°C.

渗透泵控释片是制药行业的新剂型,因恒定的释药速率对疗效的明显提升而受到青睐.释药孔决定控释片的溶出度,而释药孔的成型方法中激光打孔优势明显.在研制的专用激光打孔设备上进行了释药孔的打孔实验研究,确定了离焦量、激光电流、激光脉宽等参数所起的不同作用.发现离焦量主要影响孔径;激光电流(激光功率)主要影响碳化层;激光脉宽主要影响孔深等.这些现象和规律对提高渗透泵控释片激光打孔的效率和质量具有指导或参考作用,对发展渗透泵控释片产业非常有意义.

CFCs, HCFCs are stipulated to phase out, and other alternative refrigerants like R134a, are also constrained as a result from their high GWP values. CO2 as a natural working fluid now is used in reciprocating compressors due to its uniquely beneficial properties (ozone depletion potential, ODP=0; global warming potential, GWP =1). However, one remarkable characteristics of the CO2 reciprocating compressor operated in trans-critical region is the high operating pressure, which may impose high pressure loads on the connecting–rod big end bearing, further on the crankshaft journal bearings through the slider-crank mechanism. The work presented here is trying to study the friction losses of crankshaft journal bearings in a CO2 reciprocating compressor, by using a multiple regression method developed by Stachowiak and Batchelor(2001). The bearing performances depend mostly on the oil viscosity. In this case, the solubility of the CO2 into the lubricating oil is taken into consideration, which affects the oil viscosity.