HVAC system size – getting it right

There is evidence that many heating, ventilating & air conditioning (HVAC) systems, installed in larger buildings, have more capacity than is ever required to keep the occupants comfortable. This paper explores the reasons why this can occur, by examining a typical brief/design/documentation process. Over-sized HVAC systems cost more to install and operate and may not be able to control thermal comfort as well as a “right-sized” system. These impacts are evaluated, where data exists. Finally, some suggestions are developed to minimise both the extent of, and the negative impacts of, HVAC system over-sizing, for example: • Challenge “rules of thumb” and/or brief requirements which may be out of date. • Conduct an accurate load estimate, using AIRAH design data, specific to project location, and then resist the temptation to apply “safety factors • Use a load estimation program that accounts for thermal storage and diversification of peak loads for each zone and air handling system. • Select chiller sizes and staged or variable speed pumps and fans to ensure good part load performance. • Allow for unknown future tenancies by designing flexibility into the system, not by over-sizing. For example, generous sizing of distribution pipework and ductwork will allow available capacity to be redistributed. • Provide an auxiliary tenant condenser water loop to handle high load areas. • Consider using an Integrated Design Process, build an integrated load and energy use simulation model and test different operational scenarios • Use comprehensive Life Cycle Cost analysis for selection of the most optimal design solutions. This paper is an interim report on the findings of CRC-CI project 2002-051-B, Right-Sizing HVAC Systems, which is due for completion in January 2006

Perturbing Conformal Turbulence

We consider perturbations of the non-unitary minimal model solutions of two-dimensional conformal turbulence proposed by Polyakov. Demanding the absence of non-integrable singularities in the resulting theories leads to constraints on the dimension of the perturbing operator. We give some general solutions of these constraints, illustrating with examples of specific models. We also examine the effect of such perturbations on the Hopf equation and derive the interesting result that the latter is invariant under a certain class of perturbations, to first order in perturbation theory, examples of which are given in specific cases.Comment: uuencoded ps file, 13 page

An area-time efficient FPGA-implementation of online finite-set model based predictive controllers for flying capacitor inverters

Recently there has been an increase in the use of model-based predictive control (MBPC) for power-electronic converters. Especially for flying-capacitor multilevel converters (FCC) this offers an interesting possibility to simultaneously control output current and the capacitor voltages. The computational burden however is very high and often restrictive for a good implementation. In this paper a time and resource efficient design methodology is presented for the FPGA implementation of FCC MBPC. The control is fully implemented in programmable digital logic. Due to a parallel processing for the three converter phases and a fully pipelined calculation of the prediction stage an area-time efficient implementation is realized. Furthermore, this is achieved by using a high-level design tool. The implementation aspects for 3, 4 and 5-level FC inverters are discussed, with a focus on the 4-level case

Beyond the Standard Embedding in M-Theory on S^1/Z_2

In this paper we discuss compactifications of M-theory to four dimensions on X \times S^1/Z_2, in which nonstandard embeddings in the E_8 \times E_8 vacuum gauge bundle are considered. At the level of the effective field theory description of Horava and Witten, this provides a natural extension of well known results at weak coupling, to strongly coupled E_8 \times E_8 heterotic strings. As an application of our results, we discuss models which exhibit an anomalous U(1)_A symmetry in four dimensions, and show how this emerges from the reduction of the d = 11 toplogical term C \wedge G \wedge G, and how it is consistent with d = 4 anomaly cancellation in M-theory. As a further application of nonstandard embeddings, we show how it is possible to obtain an inverse hierarchy of gauge couplings, where the observable sector is more strongly coupled than the hidden one. The basic construction and phenomenological viability of these scenarios is demonstrated.Comment: 32 pages, LaTex, no figures, references adde

The Stability of Self Assessed Health Status

The use of self assessed health status as a measure of health is common in empirical research. We analyse a unique Australian survey in which a random sub-sample of respondents answer a standard self assessed health question twice -- before and after an additional set of health related questions. 28% of respondents change their reported health status. Response instability is related to age, income and occupation. We also compare the responses of these individuals to other respondents who are queried only once. The distributions of responses to both questions by the former group are statistically different from the distribution of responses by the latter group.self-assessed health status

Crime and the Quality of Life in Wisconsin Counties

The impact of crime on the local quality of life of a region is examined. Using the methods suggested by Roback (1982) hedonic pricing analysis is used to examine the effects of eight categories of crime on property values and wages. The hedonic results are then used to calculate the implicit prices of the various types of crime. Prices are computed for both urban and rural areas reflecting differences in lifestyle and the corresponding impact of crime. As expected, crime has a measurable negative cost and lowers overall quality of life in a region and the level of impact varies significantly by type of crime.