Kidney transplantation is the optimal treatment for end-stage kidney disease. Retrieval, transport and transplant of kidney grafts causes ischaemia reperfusion injury. The current accepted standard ...is static cold storage (SCS) whereby the kidney is stored on ice after removal from the donor and then removed from the ice box at the time of implantation. However, technology is now available to perfuse or "pump" the kidney during the transport phase or at the recipient centre. This can be done at a variety of temperatures and using different perfusates. The effectiveness of treatment is manifest clinically as delayed graft function (DGF), whereby the kidney fails to produce urine immediately after transplant.
To compare hypothermic machine perfusion (HMP) and (sub)normothermic machine perfusion (NMP) with standard SCS.
We searched the Cochrane Kidney and Transplant Register of Studies to 18 October 2018 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.
All randomised controlled trials (RCTs) and quasi-RCTs comparing HMP/NMP versus SCS for deceased donor kidney transplantation were eligible for inclusion. All donor types were included (donor after circulatory (DCD) and brainstem death (DBD), standard and extended/expanded criteria donors). Both paired and unpaired studies were eligible for inclusion.
The results of the literature search were screened and a standard data extraction form was used to collect data. Both of these steps were performed by two independent authors. Dichotomous outcome results were expressed as risk ratio (RR) with 95% confidence intervals (CI). Continuous scales of measurement were expressed as a mean difference (MD). Random effects models were used for data analysis. The primary outcome was incidence of DGF. Secondary outcomes included: one-year graft survival, incidence of primary non-function (PNF), DGF duration, long term graft survival, economic implications, graft function, patient survival and incidence of acute rejection.
No studies reported on NMP, however one ongoing study was identified.Sixteen studies (2266 participants) comparing HMP with SCS were included; 15 studies could be meta-analysed. Fourteen studies reported on requirement for dialysis in the first week post-transplant (DGF incidence); there is high-certainty evidence that HMP reduces the risk of DGF when compared to SCS (RR 0.77; 95% CI 0.67 to 0.90; P = 0.0006). HMP reduces the risk of DGF in kidneys from DCD donors (7 studies, 772 participants: RR 0.75; 95% CI 0.64 to 0.87; P = 0.0002; high certainty evidence), as well as kidneys from DBD donors (4 studies, 971 participants: RR 0.78, 95% CI 0.65 to 0.93; P = 0.006; high certainty evidence). The number of perfusions required to prevent one episode of DGF (number needed to treat, NNT) was 7.26 and 13.60 in DCD and DBD kidneys respectively. Studies performed in the last decade all used the LifePort machine and confirmed that HMP reduces the incidence of DGF in the modern era (5 studies, 1355 participants: RR 0.77, 95% CI 0.66 to 0.91; P = 0.002; high certainty evidence). Reports of economic analysis suggest that HMP can lead to cost savings in both the North American and European settings.Two studies reported HMP also improves graft survival however we were not able to meta-analyse these results. A reduction in incidence of PNF could not be demonstrated. The effect of HMP on our other outcomes (incidence of acute rejection, patient survival, hospital stay, long-term graft function, duration of DGF) remains uncertain.
HMP is superior to SCS in deceased donor kidney transplantation. This is true for both DBD and DCD kidneys, and remains true in the modern era (studies performed in the last decade). As kidneys from DCD donors have a higher overall DGF rate, fewer perfusions are needed to prevent one episode of DGF (7.26 versus 13.60 in DBD kidneys).Further studies looking solely at the impact of HMP on DGF incidence are not required. Follow-up reports detailing long-term graft survival from participants of the studies already included in this review would be an efficient way to generate further long-term graft survival data.Economic analysis, based on the results of this review, would help cement HMP as the standard preservation method in deceased donor kidney transplantation.RCTs investigating (sub)NMP are required.
The magnetocaloric effect and its most straightforward application, magnetic refrigeration, are topics of current interest due to the potential improvement of energy efficiency of cooling and ...temperature control systems, in combination with other environmental benefits associated to a technology that does not rely on the compression/expansion of harmful gases. This review presents the fundamentals of the effect, the techniques for its measurement with consideration of possible artifacts found in the characterization of the samples, a comprehensive and comparative analysis of different magnetocaloric materials, as well as possible routes to improve their performance. An overview of the different magnetocaloric prototypes found in literature as well as alternative applications of the magnetocaloric effect for fundamental studies of phase transitions are also included.
•A combined cooling and desalination unit is proposed.•The unit recovers geothermal heat of oilfield in high water cut stage.•Cooling is produced by an ejector expansion CO2 refrigeration ...cycle.•Output power of the CO2 power cycle runs the refrigerator compressor.•Rejected heat of both cycles is used by a HDH desalination unit.•Payback period of the energy system varies between 7.65 and 8.25 years.
Onshore oilfields are considered as geothermal fields producing hot water in the high water cut stage (HWCS). In the present study, a supercritical CO2 power cycle is proposed to recover the heat of the hot water obtained at a temperature close to 140 °C from the oilfield in the HWCS. The output power of the supercritical CO2 power cycle is expensed to run the compressor of an ejector expansion CO2 refrigeration cycle. Rejected heat of CO2 cycles is partially utilized by the HDH (Humidification-dehumidification) desalination unit. It is observed that though there exists an optimum turbine back pressure (TBP) corresponding to a maximum refrigeration effect, fresh water production rate increases with an increasing TBP. However, for each specified evaporator temperature, there is an optimum TBP corresponding to the minimum payback period (PP) of the energy system. The optimum TBP is close to 8.4 MPa for all considered evaporator temperatures and corresponding values of PP varies between 7.65 and 8.25 years. For an evaporator temperature of −15 °C, the refrigeration effect and fresh water production rate are 380.32 kW and 0.349 kg/s, respectively. The proposed energy system is capable of partially satisfying localized energy services like cooling and fresh water supply.
Magnetic refrigeration technology based on the magnetocaloric effect (MCE) of magnetic substances has been considered a prominent, energy‐efficient, and environmentally benign cooling method. ...Exploring suitable magnetic substances is a prerequisite for practical applications. A family of rare‐earth‐free magnetocaloric materials called Mn30Fe20−xCuxAl50 alloys is identified room‐temperature refrigeration, which are derived from the well‐known MnAl‐based permanent magnets. As expected from experimental and theoretical investigations, all of the Mn30Fe20−xCuxAl50 alloys are crystallized in a stable cubic CsCl‐type crystal structure, revealing a single second‐order type magnetic phase transition (MPT) with tunable MPT temperature. They also exhibit a large reversible MCE and good magnetocaloric performances in a wide temperature range. Crucially, these Mn30Fe20−xCuxAl50 alloys represent a rare case of magnetic materials belonging to a large family that can be fabricated from low‐price, earth‐abundant, and non‐toxic elements. They could provide new choices for practical room‐temperature magnetic refrigeration applications.
The achievement of good magnetocaloric performances is reported in the Mn30Fe20‐xCuxAl50 alloys with a stable cubic CsCl‐type structure which are derived from the family of MnAl‐based permanent magnets. These alloys represent a rare case of magnetocaloric materials that can be fabricated from low‐price, earth‐abundant, and non‐toxic elements, which could provide new choices for room‐temperature refrigeration.
•Experimental investigations established the performance characteristics of CO2 gas coolers.•CFD modelling is able to adequately represent the heat transfer characteristics of gas coolers.•A ...horizontal slit fin can improve gas cooler performance by 7%.•Refrigerant side heat transfer coefficient varies significantly along the tubes of the gas cooler.•Variation of refrigerant side heat transfer coefficient should be taken into account in gas cooler design and modelling.
Gas coolers are heat rejection heat exchangers in vapour compression refrigeration systems that use carbon dioxide (CO2) as refrigerant. The design of gas coolers has a significant influence on the performance of CO2 refrigeration systems as it determines to a large extent the gas cooler/condenser pressure and the power consumption of the system. This paper investigates local refrigerant and air heat transfer coefficients in plain fin-and-tube gas cooler coils using Computational Fluid Dynamics (CFD) modelling. The aims were to provide insights into the variation of the local heat transfer rates in the coil and determine the influence of a) design enhancements such as the use of slit fins and b) to develop correlations for overall refrigerant and air heat transfer coefficients to be used in CO2 refrigeration component and system modelling. The results from the model which was validated against experimental measurements showed that a horizontal slit on the fin between the first and second row of tubes can lead to an increase in the heat rejection rate of the gas cooler by between 6% and 8%. This in turn can lead to smaller heat exchanger heat transfer area for a given heat rejection capacity or lower high side pressure and higher efficiency for the refrigeration system. The results and heat transfer correlations developed are a valuable resource for researchers and manufacturers of CO2 and other heat exchanger coils that experience a wide variation in refrigerant temperature during the gas cooling process.
Refrigeration systems in industrial food processing plants are large users of electric energy and often show high peak power consumption. Cold thermal energy storage (CTES) technology integrated into ...refrigeration systems can reduce the peak power requirement and achieve peak shifting by decoupling the supply and demand of the refrigeration load. This paper presents the design and performance of a CTES unit consisting of a pillow plate heat exchanger (PP-HEX) immersed into a low-temperature phase change material (PCM) as the storage medium. It is one of the first experimental investigations featuring a large-scale technical solution that allows for coupling the evaporation and condensation processes of the refrigeration system with the melting and solidification of a low-temperature PCM in the same heat exchanger. The charging and discharging performance of the plates-in-tank CTES unit was extensively tested using CO2 as the refrigerant and a commercial PCM with phase change temperature of -9.6 °C. The charging time was found to be mainly affected by the refrigerant evaporation temperature, while the discharging rate and discharged energy over the cycle was higher when increasing the refrigerant condensing temperature. Using a plate pitch of 30 mm resulted in the highest mean discharge rate and total discharged energy over the cycle with 9.79 kW and 17.04 kWh, respectively. The flexible CTES-PCM unit can be adapted to fit several refrigeration load characteristics and temperature levels by changing the PP-HEX geometry and type of PCM used as the storage medium.
•Design of a cold thermal energy storage unit for CO2 refrigeration systems.•Characterisation of a commercial organic PCM.•Investigation of the charging and discharging performance for two geometries.•Condensation and evaporation temperature of CO2 are the most critical parameters.•Maximum discharged energy is 17.04 kWh over 105 min with a mean rate of 9.79 kW.
Energy-efficient and environment-friendly elastocaloric refrigeration, which is a promising replacement of the conventional vapor-compression refrigeration, requires extraordinary elastocaloric ...properties. Hitherto the largest elastocaloric effect is obtained in small-size films and wires of the prototype NiTi system. Here, we report a colossal elastocaloric effect, well exceeding that of NiTi alloys, in a class of bulk polycrystalline NiMn-based materials designed with the criterion of simultaneously having large volume change across phase transition and good mechanical properties. The reversible adiabatic temperature change reaches a strikingly high value of 31.5 K and the isothermal entropy change is as large as 45 J kg^{-1} K^{-1}. The achievement of such a colossal elastocaloric effect in bulk polycrystalline materials should push a significant step forward towards large-scale elastocaloric refrigeration applications. Moreover, our design strategy may inspire the discovery of giant caloric effects in a broad range of ferroelastic materials.
•ORC-ARC and ORC-ERC driven by low-temperature waste heat are investigated.•Thermodynamic models of basic ORC, ORC-ARC, and ORC-ERC are developed.•Exergy efficiencies of ORC, ORC-ARC, and ORC-ERC are ...parametrically simulated.•Suitable application conditions of ORC-ARC and ORC-ERC are reported.
There is large amount of waste heat resources in industrial processes. However, most low-temperature waste heat is directly discharged into the environment. With the advantages of being energy-efficient, enabling investment-savings and being environmentally friendly, the Organic Rankine Cycle (ORC) plays an important role in recycling energy from low-temperature waste heat. In this study, the ORC system driven by industrial low-temperature waste heat was analyzed and optimized. The impacts of the operational parameters, including evaporation temperature, condensation temperature, and degree of superheat, on the thermodynamic performances of ORC system were conducted, with R113 used as the working fluid. In addition, the ORC-based cycles, combined with the Absorption Refrigeration Cycle (ARC) and the Ejector Refrigeration Cycle (ERC), were investigated to recover waste heat from low-temperature flue gas. The uncoupled ORC-ARC and ORC-ERC systems can generate both power and cooling for external uses. The exergy efficiency of both systems decreases with the increase of the evaporation temperature of the ORC. The net power output, the refrigerating capacity and the resultant exergy efficiency of the uncoupled ORC-ARC are all higher than those of the ORC-ERC for the evaporation temperature of the basic ORC >153°C, in the investigated application. Finally, suitable application conditions over other temperature ranges are also given.
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•Condenser heat-driven hybrid system for T-CO2 VCRS using VERS.•Effect of pinch in generator during of phase change of VERS fluid.•Variable geometry ejector is used for VERS.•R32 is ...proposed as VERS fluid in the hybrid system.•10–50% improvement in cooling capacity of hybrid system over primary T-CO2 VCRS.
The paper presents analysis of a hybrid transcritical CO2 (T-CO2) refrigeration cycle coupled with a heat-driven vapor ejector refrigeration cycle. The heat generated by compression of CO2 in the transcritical vapor compression refrigeration system (VCRS) is utilized to drive the secondary vapor ejector refrigeration system (VERS). The performance of the hybrid system is evaluated by maintaining identical evaporator temperatures for both T-CO2 VCRS and VERS. Cooling capacity and COP of the VERS is influenced by heat recovered from T-CO2 system, thus, limiting the choice of working fluids for the VERS. Analytical model based on conservation of mass, momentum and energy, incorporating real gas behavior is used for arriving at an optimum ejector geometry used in the VERS. Amongst the five fluids analyzed, R32 is found to be most suitable for the VERS used in the hybrid system. R32 provides the highest coefficient of performance (COP) and cooling capacity by recovering maximum heat from the generator, while, other fluids yield nearly identical performance. The proposed hybrid system using R32 provides significant improvement in system performance ranging from 10 to 50% in cooling capacity over the baseline T-CO2 system for the range of evaporating temperatures from −2.5 °C to 12.5 °C.
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