A heat pump water heater (HPWH) operates on an electrically driven vapor-compression cycle and pumps energy from the air in its surroundings to water in a storage tank, thus raising the temperature ...of the water. HPWHs are a promising technology in both residential and commercial applications due to both improved efficiency and air conditioning benefits.
Residential HPWH units have been available for more than 20 years, but have experienced limited success in the marketplace. Commercial-scale HPWHs are also a very promising technology, while their present market share is extremely low.
This study dealt with reviewing HPWH systems in terms of energetic and exergetic aspects. In this context, HPWH technology along with its historical development was briefly given first. Next, a comprehensive review of studies conducted on them were classified and presented in tables. HPWHs were then modeled for performance evaluation purposes by using energy and exergy analysis methods. Finally, the results obtained were discussed. It is expected that this comprehensive review will be very beneficial to everyone involved or interested in the energetic and exergetic design, simulation, analysis, performance assessment and applications of various types of HPWH systems.
•Description of the gear profile requirement for continuous-contact helical gear pumps (CCHGP).•The derivation of the kinematic flowrate for CCHGP is derived.•A proof for CCHGP cancellation of ...kinematic flow ripple is provided.•A fluid dynamic simulation model for CCHGP is presented and validated against experiments.•The simulation results provide a justification for pressure ripple generation in CCHGP.
External gear pumps are one of the most commonly used types of positive displacement machines in high pressure hydraulic control systems, fuel-injection and fuel transport systems. Despite many merits of the traditional external gear pump design with involute teeth, the significant flow non-uniformity intrinsic of such design is considered to be a detrimental aspect, since it causes undesired noise emissions and mechanical vibrations. A disruptive concept of continuous-contact helical gear pumps (CCHGP) was proposed and successfully commercialized in the recent past. Such concept was proven to have clear advantages in terms of noise emissions. However, a clear interpretation of the displacing action and the transient features of the delivery flow was never addressed in past literature. This paper addresses this gap by first discussing the family of gear profiles suitable for implementing the CCHGP design. Subsequently, an analysis on the kinematic flow ripple is given, showing how such design concept can reduce or even eliminate the kinematic flow pulsations. The paper also presents a numerical approach for modelling the operation of CCHGPs, starting from the modeling of the geometric features necessary for a fluid dynamic analysis based on a lumped parameter approach. For model validation purposes, a commercial CCHGP was tested at the authors’ research center, and the simulation results were compared against the experiments, to show the level of accuracy of the model, as well as it potentials for future design studies.
Among the many practical problems concerned with such a project, apart from tunnelling and mechanical excavation in the high Alps, are the necessity to dredge the harbour at Trieste so that it can ...eventually accommodate oil tankers of 160,000 dead weight tons; setting storage tanks there on piles because available land is a rocky hill site; construction of several thousand feet of piers in the Adriatic ...
Pump as Turbine (PAT) is an effective alternative of power generation for small hydropower system. Since the characteristic curves under turbine mode are not supplied by manufacturer of pumps, the ...theoretical model for energy performance of centrifugal turbomachinery under pump and turbine modes is proposed by means of detailed modeling of losses inside hydraulic machinery. Based on the theoretical model, a flowrate-based iteration method is proposed to determine the best efficiency point (BEP) under turbine mode. In order to validate the accuracy of established theoretical model, case studies are carried out under three centrifugal pumps, with the specific speed varied from 103 to 187, and the predicted results by theoretical model are compared with experimental measurements and numerical simulations. It is found that the average relative variations for prediction of pump head and efficiency are 6.12% and 5.51%, respectively, and they are 5.40% and 3.63% for turbine head and efficiency, which is of sufficient accuracy for engineering practice. The predicted BEP under turbine mode is also of great accuracy, with relative variation of 1.28% on average. In addition, the PAT performance as well as losses under pump and turbine modes have been analyzed in detail.
•Theoretical model of energy performance prediction for pump as turbine is proposed.•Flowrate-based iteration method of best efficiency point (BEP) determination is proposed.•Three pumps with specific speed of 103, 131 and 187 are investigated.•Losses of centrifugal pump and PAT under various flow rates are analyzed.
The paper is focused on understanding the flow losses and the resulting flow/pressure dynamics in a piston pump. Initially, equations to evaluate leakages in all piston pump gaps will be presented ...and tested against numerical models, later the equations will be linked to determine the general pressure/flow pump dynamic characteristics. The model will also provide the temporal pressure in each piston/cylinder chamber and the temporal leakage in all pump clearances. A test rig able to measure the dynamic pressure inside a piston chamber was build and employed to evaluate pressure ripple dynamics as a function of turning speed, outlet pressure and swash plate angle. The comparison between experimental and simulated results is very good, giving confidence to the model presented. The advantage of using the analytical approach is that explicit equations allow a more direct understanding of the effect of dimension changes and operating conditions on pump dynamics. Fluid used hydraulic oil ISO 32.
During the last decade, a number of studies have been conducted by various investigators in the design, modeling and testing of solar assisted heat pump systems (SAHPSs). This paper reviews the ...studies conducted on the energy and exergy analysis of SAHPS systems in Turkey and around the world as of the end of December 2004. The studies undertaken on the SAHPS systems are categorized into four groups as follows: (i) SAHPSs for water heating, (ii) SAHPSs with storage (conventional type) for space heating, (iii) SAHPSs with direct expansion for space heating, and (iv) Solar-assisted ground source heat pump greenhouse heating system (SAGSHPGHS). This paper investigates the studies on SAGSHPs, especially ground-source heat pumps, also known geothermal heat pumps, at the Turkish universities in more detail, by giving Turkey's solar energy potential.
An artificial molecular pump Cheng, Chuyang; McGonigal, Paul R; Schneebeli, Severin T ...
Nature nanotechnology,
06/2015, Letnik:
10, Številka:
6
Journal Article
Recenzirano
Carrier proteins consume fuel in order to pump ions or molecules across cell membranes, creating concentration gradients. Their control over diffusion pathways, effected entirely through noncovalent ...bonding interactions, has inspired chemists to devise artificial systems that mimic their function. Here, we report a wholly artificial compound that acts on small molecules to create a gradient in their local concentration. It does so by using redox energy and precisely organized noncovalent bonding interactions to pump positively charged rings from solution and ensnare them around an oligomethylene chain, as part of a kinetically trapped entanglement. A redox-active viologen unit at the heart of a dumbbell-shaped molecular pump plays a dual role, first attracting and then repelling the rings during redox cycling, thereby enacting a flashing energy ratchet mechanism with a minimalistic design. Our artificial molecular pump performs work repetitively for two cycles of operation and drives rings away from equilibrium toward a higher local concentration.
The ability to silence the activity of genetically specified neurons in a temporally precise fashion would provide the opportunity to investigate the causal role of specific cell classes in neural ...computations, behaviours and pathologies. Here we show that members of the class of light-driven outward proton pumps can mediate powerful, safe, multiple-colour silencing of neural activity. The gene archaerhodopsin-3 (Arch) from Halorubrum sodomense enables near-100% silencing of neurons in the awake brain when virally expressed in the mouse cortex and illuminated with yellow light. Arch mediates currents of several hundred picoamps at low light powers, and supports neural silencing currents approaching 900 pA at light powers easily achievable in vivo. Furthermore, Arch spontaneously recovers from light-dependent inactivation, unlike light-driven chloride pumps that enter long-lasting inactive states in response to light. These properties of Arch are appropriate to mediate the optical silencing of significant brain volumes over behaviourally relevant timescales. Arch function in neurons is well tolerated because pH excursions created by Arch illumination are minimized by self-limiting mechanisms to levels comparable to those mediated by channelrhodopsins or natural spike firing. To highlight how proton pump ecological and genomic diversity may support new innovation, we show that the blue-green light-drivable proton pump from the fungus Leptosphaeria maculans (Mac) can, when expressed in neurons, enable neural silencing by blue light, thus enabling alongside other developed reagents the potential for independent silencing of two neural populations by blue versus red light. Light-driven proton pumps thus represent a high-performance and extremely versatile class of 'optogenetic' voltage and ion modulator, which will broadly enable new neuroscientific, biological, neurological and psychiatric investigations.
•A dual-source (air and ground) inverter driven heat pump (DSHP) is presented.•The dynamic model of the DSHP has been made with TRNSYS.•DSHP reduces the ground temperature drift due to unbalanced ...building loads.•DSHP can work with shorter borehole (BHE) fields (up to 50%).•The optimal switching (air-ground) temperature depends on the size of BHEs.
In this paper the energy performance of a Dual-Source Heat Pump (DSHP) system able to use both air and ground as external heat source is analysed by using TRNSYS and the experimental data obtained by testing a DSHP prototype. The DSHP seasonal and annual performance factors are compared with those offered by the same DSHP in which only ground (ground-source mode) or only external air (air-source mode) is used as external heat source in order to evaluate the benefits achievable with the exploitation of a double external heat source (ground and air) with the same unit. Yearly dynamic simulations have been carried out by coupling the DSHP to a detached residential building located in Bologna, characterized by unbalanced heating and cooling loads, and coupled to a geothermal loop based on borehole heat exchangers (BHEs). With the help of the dynamic simulations it has been demonstrated that DSHPs can be very useful in order to solve the problems linked to the ground temperature drift which can be originated by the presence of an undersized borehole heat exchanger field and/or by unbalanced heating and cooling loads. In fact, the use of external air as auxiliary heat source with respect to ground during the most severe season enables to obtain more stable energy performance even in presence of undersized BHEs. In this paper it is shown how an optimal trade-off in terms of annual energy performance and investment costs can be obtained by reducing the size of the DSHP borehole field of 15–55% with respect to the borehole field needed by a conventional ground-coupled heat pump having the same size. In this way the DSHP can be used during the retrofitting of thermal plants based on ground-coupled heat pumps in which an undersized BHEs field is present.
To promote the development and application of the liquid–gas jet pump (LGJP), the research status of its design theory, internal flow mechanism, structural optimization and practical application are ...reviewed. The development history of the LGJP is briefly reviewed, the latest research and application progress of the LGJP is introduced, and the pulse-type of LGJP, especially the centrifugal jet vacuum pump (CJVP), is emphatically discussed. The research and development direction of the LGJP is analyzed and proposed: CFD will be more deeply applied to the mechanism research and performance improvement of the LGJP; the diversity and heterogeneity of the fluid medium and its influence on the internal flow mechanism are the research highlights of the LGJP; it is urgent to study the gas–liquid two-phase flow and pumping mechanism inside the pulsed liquid–gas jet pump (PLGJP), especially the CJVP.
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