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.
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•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.
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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 ...
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4.
Leviathan and the air-pump Shapin, Steven; Schaffer, Simon
2011., 20110815, 2011, 2011-08-15, Volume:
32
eBook
Leviathan and the Air-Pump examines the conflicts over the value and propriety of experimental methods between two major seventeenth-century thinkers: Thomas Hobbes, author of the political treatise ...Leviathan and vehement critic of systematic experimentation in natural philosophy, and Robert Boyle, mechanical philosopher and owner of the newly invented air-pump. The issues at stake in their disputes ranged from the physical integrity of the air-pump to the intellectual integrity of the knowledge it might yield. Both Boyle and Hobbes were looking for ways of establishing knowledge that did not decay into ad hominem attacks and political division. Boyle proposed the experiment as cure. He argued that facts should be manufactured by machines like the air-pump so that gentlemen could witness the experiments and produce knowledge that everyone agreed on. Hobbes, by contrast, looked for natural law and viewed experiments as the artificial, unreliable products of an exclusive guild.
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.
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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.
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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.
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8.
An artificial molecular pump Cheng, Chuyang; McGonigal, Paul R; Schneebeli, Severin T ...
Nature nanotechnology,
06/2015, Volume:
10, Issue:
6
Journal Article
Peer reviewed
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.
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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.
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•Noise subtraction is proposed to denoise the vibration signals of axial and centrifugal pump.•Marginal band selection indicator (MBSI) is proposed to select the spectral frequency band having defect ...information.•Marginal enhanced square envelope spectrum (MESES) is computed from the selected spectral frequency band.•The proposed MBSI indicator is sensitive to cyclic impulses produces due to bearing defect.•The proposed MBSI is superior in comparison to the existing l2/l1 norm indicator.
The natural intermittent impulses created by impeller in case of centrifugal pump, and reciprocating motions of piston in case of axial pump exhibit strong cyclo-stationary phenomenon. This makes the identification of defect impulses difficult in their vibration signals even with the powerful signal processing techniques such as Fast-spectral correlation. To deal with the issue, this work proposes noise subtraction and marginal enhanced square envelope spectrum (MESES) for detecting bearing defects in the centrifugal and axial pump. For subtraction of noise, Fast Fourier Transform (FFT) of signal of unknown defect condition is computed and then FFT of normal working condition is subtracted from the signal of unknown defect condition. Then, inverse FFT is applied to resulting signal to construct denoised signal in time domain. The noise subtraction is done in frequency domain so as to avoid time lag problem which generally occurs in two signals obtained at different time. Further, the signal is processed by Fast- spectral correlation. To select the spectral frequency having fault related information, a criterion named as marginal band selection indicator (MBSI) is proposed. The spectral frequency band having the highest MBSI is selected for computing MESES. After selection of spectral frequency, MESES is computed and Feature frequency is find out. Finally, comparison of feature frequency is done with the bearing fundamental fault frequencies to conform the presence of defect.
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