| 1. |
- Borgström, Karin Margaretha, 1956-
(författare)
-
Determination of the thermal conductivity of the insulation in district heating mains : Field measurements
- 1994
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns the development of a measurement method for determination in the field of the thermal conductivity of the insulation in buried district heating mains. The thermal conductivity of the insulation is calculated from the measured value of the radial heat flow through the heating main, the measured temperature difference across the insulation, and the dimensions of the heating main. The heat flow has been measured with a heat flux sensor which was fitted to the surface of the casing. The temperature has been measured with copper/constantan thermocouples. It is a necessary condition for the method used in the project for determination of the thermal conductivity of the heating main insulation that the heating main is uncovered and is not in contact with the surrounding soil over a distance of about 1.5 m and that the measurements are made directly on the heating main. In this way, no account need be taken of the material surrounding the heating main, nor of the effect of this material on the measurements. No interference is needed with the heating main which would affect the distribution of the district heating water, and the heating main can remain in operation during measurements. Shielding insulation consisting of preformed insulation sections which were placed over the casing of the heating main and covered the heat flux sensor and some of the casing. The function of this insulation was to shield the heat flux sensor from external thermal disturbances. In the field measurements, a copper guard plate of 0.5 mm thickness, the temperature of which could be adjusted, was also placed over the shielding insulation in order to maintain the temperature on the heat flux sensor as constant as possible. When temperature and heat flow are measured, the instruments used will be affected by conditions which prevail at the time of measurement. It is therefore very important to analyse the sources of error which may arise in the measuring situation at hand. The effect of these factors on the measured values has been studied by ' laboratory measurements ' theoretical calculations ' field measurements On the basis of the resulting values of heat flows and temperatures obtained in field measurements on plastic heating mains which were operating under normal conditions, the thermal conductivity of the insulation of the main has been estimated. The method has been tested on plastic heating mains with directly foamed insulation, since this is the most common type of heating main both in the existing district heating network and in new construction. The measuring method can also be used on other circular heating mains.
|
|
| 2. |
- Jonsson, Magnus, 1969-
(författare)
-
High performance fiber-optic interconnection networks for real-time computing systems
- 1999
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Parallel and distributed computing systems become more and more powerful and hence place increasingly higher demands on the networks that interconnect their processors or processing nodes. Many of the applications running on such systems, especially embedded systems applications, have real-time requirements and, with increasing application demands, high-performance networks are the hearts of these systems. Fiber-optic networks are good candidates for use in such systems in the future. This thesis contributes to the relatively unexplored area of fiber-optic networks for parallel and distributed real-time computer systems and suggests and evaluates several fiber-optic networks and protocols. Two different technologies are used in the networks, WDM (Wavelength Division Multiplexing) and fiber-ribbon point-to-point links. WDM offers multiple channels, each with a capacity of several Gbit/s. A WDM star network in which protocols and services are efficiently integrated to support different kinds of real-time demands, especially hard ones, has been developed. The star-of-stars topology can be chosen to offer better network scalability. The WDM star architecture is attractive but its future success depends on components becoming more commercially mature. Fiber-ribbon links, offering instead an aggregated bandwidth of several Gbit/s, have already reached the market with a promising price/performance ratio. This has motivated the development and investigation of two new ring networks based on fiber-ribbon links. The networks take advantage of spatial bandwidth reuse, which can greatly enhance performance in applications with a significant amount of nearest downstream neighbor communication. One of the ring networks is control channel based and not only has support for real-time services like the WDM star network but also low level support for, e.g., group communication. The approach has been to develop network protocols with support for dynamic real-time services, out of time-deterministic static TDMA systems. The focus has been on functionality more than pure performance figures, mostly on real-time features but also on other types of functionality for parallel and distributed systems. Worst-case analyses, some simulations, and case studies are reported for the networks. The focus has been on embedded supercomputer applications, where each node itself can be a parallel computer, and it is shown that the networks are well suited for use in the radar signal processing systems studied. Other application examples in which these kinds of networks are valuable are distributed multimedia systems, satellite imaging and other image processing applications.
|
|
