Feasibility of Municipal Water Mains as Heat Sink for Residential Air-Conditioning

It has been proposed that municipal water mains be used as the heat sink or the heat source for air-conditioning or heating, respectively. This paper addresses the extent of thermal contamination associated with the use of municipal water in the mains for heat rejection in residential air-conditioning applications. A small residential neighborhood in Austin, Texas was selected, and typical residential a/c loads and measured water supply rates in the main were used in the assessment. Very substantial increases in water temperature occur in the mains for air-conditioning, even if a modest fraction of the residents opt to install such systems. No more than 1 to 2 % of residents could adopt such systems before water temperature rises in the mains become significant. The general conclusion is that, while the benefit to an individual using this concept may be positive, the impact on water temperature is excessive

Analytical and experimental study of stratification and liquid-ullage coupling, 1 June 1964 - 31 May 1965

Closed-form solution for stratification of subcooled fluids in containers subjected to heating, and for liquid-ullage vapor couplin

Microscopic energy flows in disordered Ising spin systems

An efficient microcanonical dynamics has been recently introduced for Ising spin models embedded in a generic connected graph even in the presence of disorder i.e. with the spin couplings chosen from a random distribution. Such a dynamics allows a coherent definition of local temperatures also when open boundaries are coupled to thermostats, imposing an energy flow. Within this framework, here we introduce a consistent definition for local energy currents and we study their dependence on the disorder. In the linear response regime, when the global gradient between thermostats is small, we also define local conductivities following a Fourier dicretized picture. Then, we work out a linearized "mean-field approximation", where local conductivities are supposed to depend on local couplings and temperatures only. We compare the approximated currents with the exact results of the nonlinear system, showing the reliability range of the mean-field approach, which proves very good at high temperatures and not so efficient in the critical region. In the numerical studies we focus on the disordered cylinder but our results could be extended to an arbitrary, disordered spin model on a generic discrete structures.Comment: 12 pages, 6 figure

Shot Noise in Linear Macroscopic Resistors

We report on a direct experimental evidence of shot noise in a linear macroscopic resistor. The origin of the shot noise comes from the fluctuation of the total number of charge carriers inside the resistor associated with their diffusive motion under the condition that the dielectric relaxation time becomes longer than the dynamic transit time. Present results show that neither potential barriers nor the absence of inelastic scattering are necessary to observe shot noise in electronic devices.Comment: 10 pages, 5 figure

A Comparison of Domestic Water Heating Options in the Austin Electric Service Area

This report examines the energy, demand, and economic effects of three alternative electric water heating systems from the perspective of both the City of Austin Electric Utility and its ratepayers. An hourly computer simulation was used to model the operation of (1) a conventional electric resistance water heater (ERWH), (2) a heat pump water heater (HPWH), and (3) a heat recovery water heater (HRWH). Data from a previously conducted field test of solar water heaters (SWH) in the Austin area was used to compare this fourth water heating option. In the base case, the SWH was found to save the most energy relative to a conventional ERWH followed by the HPWH and the HRWH, respectively. However, under most economic assumptions thought to be reasonable for the Austin area, the heat recovery water heater appeared to be the best choice for the Austin all-electric ratepayer. From the Utility's perspective, it was determined that: (1) widespread ratepayer use of heat recovery water heater systems would be beneficial to the Utility; (2) ratepayer use of solar water heater systems would be marginally beneficial to the Utility; and (3) ratepayer use of heat pump water heater systems would not be beneficial to the Utility

The Relation Between Galaxy ISM and Circumgalactic OVI Gas Kinematics Derived from Observations and Λ\LambdaCDM Simulations

We present the first galaxy-OVI absorption kinematic study for 20 absorption systems (EW>0.1~{\AA}) associated with isolated galaxies (0.15$<z<$0.55) that have accurate redshifts and rotation curves obtained using Keck/ESI. Our sample is split into two azimuthal angle bins: major axis ($\Phi<25^{\circ}$) and minor axis ($\Phi>33^{\circ}$). OVI absorption along the galaxy major axis is not correlated with galaxy rotation kinematics, with only 1/10 systems that could be explained with rotation/accretion models. This is in contrast to co-rotation commonly observed for MgII absorption. OVI along the minor axis could be modeled by accelerating outflows but only for small opening angles, while the majority of the OVI is decelerating. Along both axes, stacked OVI profiles reside at the galaxy systemic velocity with the absorption kinematics spanning the entire dynamical range of their galaxies. The OVI found in AMR cosmological simulations exists within filaments and in halos of ~50 kpc surrounding galaxies. Simulations show that major axis OVI gas inflows along filaments and decelerates as it approaches the galaxy while increasing in its level of co-rotation. Minor axis outflows in the simulations are effective within 50-75 kpc beyond that they decelerate and fall back onto the galaxy. Although the simulations show clear OVI kinematic signatures they are not directly comparable to observations. When we compare kinematic signatures integrated through the entire simulated galaxy halo we find that these signatures are washed out due to full velocity distribution of OVI throughout the halo. We conclude that OVI alone does not serve as a useful kinematic indicator of gas accretion, outflows or star-formation and likely best probes the halo virial temperature.Comment: 24 pages, 21 figures, 4 tables. Accepted to ApJ on November 14, 201

Classical simulation of measurement-based quantum computation on higher-genus surface-code states

We consider the efficiency of classically simulating measurement-based quantum computation on surface-code states. We devise a method for calculating the elements of the probability distribution for the classical output of the quantum computation. The operational cost of this method is polynomial in the size of the surface-code state, but in the worst case scales as $2^{2g}$ in the genus $g$ of the surface embedding the code. However, there are states in the code space for which the simulation becomes efficient. In general, the simulation cost is exponential in the entanglement contained in a certain effective state, capturing the encoded state, the encoding and the local post-measurement states. The same efficiencies hold, with additional assumptions on the temporal order of measurements and on the tessellations of the code surfaces, for the harder task of sampling from the distribution of the computational output.Comment: 21 pages, 13 figure