A Gamma type Stirling refrigerator optimization: An experimental and analytical investigation

Performance study on compressed air refrigeration system based on single screw expander

With the continuous development of milling technology and the increasing number of slim hole plugging removal operations worldwide, how to guide operators to select reasonable working parameters to achieve efficient plugging removal has become a problem worth paying attention to. At present, the research on the optimization of working parameters based on the characteristics of plugging material is not complete. In order to explore the feasibility of efficient unplugging operation with low weight on bit and high rotational speed in slim hole, this paper chooses cement plug as plugging material, and uses Mechanical Specific Energy (MSE) and Rate of Penetration (ROP) as the evaluation index of plugging efficiency. A test bench was established and a low WOB milling test was designed. Meanwhile, a 3D simulation model of full-size PDC bit milling cement plug was established. Through the test and numerical simulation analysis, it is found that when the bit weight is enough to destroy the blockage, efficient operation can be realized under the working condition of low WOB and high rotational speed. A working parameter optimization method is proposed, and the recommended working interval is 3 kN WOB and 1500 ~ 2000 r/min rotational speed; 5 kN WOB, 1000 r/min rotational speed. The results show that the increase of WOB and rotational speed can improve the ROP of the bit, and it is feasible to use rotational speed to compensate the WOB to increase the ROP. In simulation and test, the efficiency of milling plugs is not good when the WOB is lower than 3 kN. To achieve high efficiency milling plugs, the priority should be to ensure that the WOB is enough to allow the cutter to normally break the plug. When analyzed with power drilling tools in conjunction with downhole motors, the ROP obtained by PDC bit with turbodrill under the condition of low WOB and high rotational speed is better than that obtained by a positive displacement motor with high WOB and low rotational speed, the results highlight the advantages of low WOB and high rotational speed milling cement plug. This paper provides a new idea for the optimization of working parameters of coiled tubing during plugging removal in slim holes.

Molten salt can acts like a storage medium or heat transfer fluid in heat recovery system. Heat transfer fluid is a fluid that has the capability to deliver heat this one side to another while heat recovery system is a system that transfers heat to produce energy. This studies shows about determining the new formulation of different molten nitrate/nitrite salts consisting of LiNO3, KNO2, KNO3 and NaNO2 that give a low temperature of melting point and high average specific heat capacity. Mixed alkaline molten nitrate/nitrite salt can act as a heat transfer fluid due to their advantageous in terms of its properties that feasible in heat recovery system such as high specific heat capacity, low vapour pressure, low cost and wide range of temperature in its application. The mixing of these primary substances will form a new line of quaternary nitrate salt (LiNO3 - KNO2 - KNO3 - NaNO2). The quaternary mixture was heated inside the box furnace at 150°C for four hours and rose up the temperature to 400°C for eight hours to homogenize the mixture. Through heating process, the elements of nitrate/nitrite base were mixed completely. The temperature was then reduced to 115°C for several hours before removing the mixture from the furnace. The melting point of each sample were testified by using thermal gravimetric analysis, TGA/DTA and experiment of determining the specific heat capacity were conducted by using Differential Scanning Calorimeter, DSC. From the result, it is found that the melting point Sample 1 with percentage of weightage (25.4wt% of LiNO3, 33.8wt% of KNO2, 20.7wt% of KNO3 and 20.1wt% of NaNO2) is 94.4°C whereas the average specific heat capacity was 1.0484/g°C while for Sample 3 with percentages of weightage (30.0wt% of LiNO3, 50.2wt% of KNO2, 3.1wt% of KNO3 and 16.7wt% of NaNO2), the melting point is 86.1°C with average specific heat capacity of 0.7274 J/g°C. In the nut shell, the quaternary mixture salts had been a good mixture with good thermal properties that low in melting point and have high specific heat capacity which could be a potential heat transfer fluid in heat recovery application.

The aim of this paper is to experimentally investigates the applying of the closed loop oscillating heat pipe (CLOHP) condenser in vapor compression refrigeration. Split type air conditioner for residence was considered with two disadvantages. Firstly, the large pressure drop was occurred in the condenser because refrigerant flows inside very small copper tube. This pressure drop causes higher compressor power, resulting in decreasing of the Coefficient of Performance (COP). Secondly, a lot of wasted heat losses to surrounding since the refrigerant has to condense after passing through condenser. To recover pressure drop and heat from the condensing process, this research is pursued to use the CLOHP instead of the conventional condenser in split type air conditioner. The refrigerating capacity, refrigerant and working fluid were 12,500 Btu/hr, R22 and R123, respectively. The experimental results were obtained then compared with the conventional one. It can be seen that COP of the conventional condenser was higher than the CLOHP condenser while energy efficiency rating (EER) of the conventional condenser was lower than the CLOHP condenser. In addition, the pressure drop in a refrigerant line of the CLOHP condenser was lower than that of the conventional condenser. Finally, 3 ℃ increasing of water temperature, which recovers heat from condenser section of CLOHP, was obtained for utilization.

Stationary shoulder friction stir welding has been used to weld 4-mm-thick 2219-T6 aluminium alloy at high rotation speeds. Strain plastic damage was applied to demonstrate the formation mechanism of welding defects at high rotation speeds above 2000 rpm. A three-way converging zone in the joint, in which materials of different microstructure characteristics converged from three directions during high tool rotation speed welding, was found. At the relatively high tool rotation speed, the significant differences in the microstructures would result in weld defects in this zone. It could be attributed to material toughness damage at high strain rate. With increasing tool rotation speed, the tensile strength of the joint constantly decreased. When the tool rotation speed varied from 2000 to 2600 rpm, the tensile strength decreased from 305 MPa (68.2% of the BM) to 238 MPa (53.2% of the BM).

The performance of the air condition system is strongly influenced by the compressor work, the condenser cooling temperature. So that the compressor working pressure (suction) and condenser cooling play a very important role in the performance of the air conditioning system which will have an impact on compressor work, compressor power, refrigeration impact, isentropic efficiency and coefficient of performance (COP) of the car air conditioning system. From the research, data will be obtained which include the pressure value on the refrigerant, namely P1 and P2, the temperature on the refrigerant, namely T1, T2, T3 and Tcabin, at the point of installation of the Manifold Gauge and Thermocouple. The research data is then processed and analyzed to obtain performance at constant rotation with variations in compressor working time both actual and theoretical as well as the efficiency of the ac system. From the results of the study, it was found that the compressor rotation was 2300 rpm with a constant rotation then measured the pressure and temperature of the refrigerant, then temperature data was obtained and analyzed to obtain the enthalpy value, thus obtaining the coefficient of performance (COP) of the car air conditioning system. The coefficient of performance (COP) of the resulting system is greater than the actual COP, the optimal COP occurs at P1 30 psi and P2 340 psi working pressures, the actual COP is 3.4848 and the theoretical COP is 4.1500, with an efficiency of 83.97% at 360 seconds.

This work has investigated the influence of change in operation conditions on the performance of a Lithium Chloride (LiCl) wheel. A rigorous experimental rig that facilitates the measurement of temperature, pressure, pressure drop, relative humidity, airflow rate and rotational speed is used. The measurements covered balanced flow at a wide range of rotational speeds (0 - 9.8 rpm), regeneration temperatures (50-70°C), airflow rates (280-540 kg/h) and relative humidities (30-65%) at ambient condition. The influence of those operation conditions on the wheel sensible effectiveness and coefficient of performance (COP) are analyzed. The result revealed that a maximum COP occurs at a rotational speed of 0.2 rpm (12 rph). The results also concluded that Kays and London correlation is sufficient in the prediction of the effectiveness of the LiCl wheel. It represents the experimental data with an average absolute percent deviation (AAPD) of 2.16 and a maximum absolute percent deviation (APDmax) of about 6.00.

Performance evaluations of an adsorption-based power and cooling cogeneration system under different operative conditions and working fluids

Experimental investigation adsorption chillers using micro-porous silica gel–water and compound adsorbent-methanol

This paper aims at deriving design recommendations for plate heat exchanger (PHE) evaporators and condensers in heat pump (HP) systems using different refrigerants. A coupled HP - PHE simulation framework was used to carry out cycle and component design for a case study, with different combinations of PHE geometrical parameters, and propane, butane and propylene/butane (0.5/0.5) as refrigerants. An operating model subsequently evaluated the heat pump thermodynamic and economic performance with the different designed PHEs: the trade-off between heat transfer area and refrigerant pressure drops was therefore taken into account for both components. Only evaporator pressure drops affected the Coefficient of Performance (COP), and different refrigerants presented dissimilar slopes of degradation. Condenser design did not influence the COP, and the economic optimum corresponded to the lowest size. The evaporator design at minimum cost was instead found as a trade-off between heat transfer area and pressure drops for all the working fluids. Despite the different rates of COP drop, the three refrigerants resulted in the same optimal pressure drop at the evaporator, equal to around 5 kPa.

In this paper, the flow ripple equation is derived to analyze the effect of working condition on pressure pulsations of an internal gear pump. Results indicate that working pressure has a significant effect on pressure fluctuation of the internal gear pump, while the rotating speed has a complex influence on the pressure pulsation behavior. Then, pressure pulsations of the internal gear pump under different working conditions are discussed by experimental investigations. Results show that the internal gear pump taken for analysis has a low-pressure pulsation at a high working pressure and a relatively high rotational speed. Regarding the frequency spectrum of the pressure pulsation, the dominant frequency is Z* fn, i.e. the product of the tooth number of the driving gear (gear shaft) and its rotational frequency for many working conditions, caused by the inevitable unsteady discharge process of gear pumps. It transforms to the rotational frequency of the gear shaft ( fn) for a high rotational speed or a high operating pressure, but to the rotating frequency of the internal gear ring (2/3 fn) only for a high operating pressure. The occurrence of the two frequencies (2/3 fn and fn) may result from the deformation of the gear ring and the gear shaft under the unbalanced radial forces caused by a high working pressure. Moreover, the frequency spectrum of the inlet pressure pulsation presents some differences from that of the outlet pressure pulsation. This is because the inlet pressure may be influenced by cavity generated at the suction side of the pump.

A combined finite element analysis and computational fluid dynamics was developed to investigate the discharge characteristics and flow field of pocket damper seals at high pressure (up to 7.2 MPa) and high rotational speed (up to 50,200 r/min) flow condition. At first, the leakage flow rates of the published experimental pocket damper seals with the eight-bladed and eight-pocket were conducted at three different pressure drops and three different rotational speeds, and a comparison between finite element analysis and computational fluid dynamics results, experimental data and computational fluid dynamics results was presented. It showed that the utilized finite element analysis/computational fluid dynamics numerical method has sufficient precision (the maximum relative deviation is less than 1.3%) to predict the leakage flow rate through the pocket damper seals. The importance of taking rotor growth with rotational speed into consideration was made apparent by the rotor growth and leakage results. Then, six pressure ratios and seven rotational speeds were utilized to study the effects of these two factors on the leakage flow characteristics of the pocket damper seals. Numerical simulation results show that the leakage through a pocket damper seals increases with decreasing pressure ratio and asymptotically approach a maximum value corresponding to the choked flow condition when the pressure ratio is small enough (less than 0.26). The leakage flow rate with and without rotor growth included both decrease with the increasing rotational speed. In addition, it is quite necessary to take rotor growth with rotational speed into consideration when the rotational speed is very high (larger than 20,200 r/min) according to the numerical results and the engineering accuracy requirement. The influence of the pressure ratio on the structure of the leakage flow field in seal cavity is negligible. A significant influence of the rotational speed on the flow field in the active cavity has been observed. The circumferential partition wall can significantly decrease the circumferential flow in active cavity of the pocket damper seals.

Rotor-stator spinning disc reactor

This paper presented the results of improvement on Coefficient of Performance (COP) of split air– conditioner which has capacity of 9000 Btu/h. This air– conditioner uses R410A as the refrigerant. COP is improved by using an innovative separated– vapor device (flash chamber) in the system. The system is designed to operate in two cases. The first case, the saturated mixture of liquid– vapor refrigerant at low pressure passes through expansion valve (using capacity tube) and enters flash chamber. The second case is that it directly enters to evaporator. Both cases were experimented in the same heat load and environmental condition. The procedure of investigation is implemented in the same different temperature in outdoor and indoor. The results show that the power consumption reduces from 3.4 % to 4.4 % and actual coefficient of performance (COP) increase from 3.8 % to 8.7 %. Besides that, pressure drop on low pressure side for two cases were also presented. Experimental results were reported to show the feasibility of an innovative separated– vapor device which can be applied in air– conditioning systems.

We investigated power requirements and pressure drop in the gas-solid stirred fluidized bed with vertical blades when increased rotational speed up to 6s-1 At high rotational speed the minimum torque for stirring was greater than predicted by the approximate equation at low rotational speed, because of the centrifugal force acting on the particles. Then we corrected the approximate equation of minimum torque for stirring by considering centrifugal force. This corrected equation correlated well with experimental values. The pressure drop at high rotational speed behaved the same as in a spouted bed.