Sparse district heating and flexible district heating pipes

The aim of this thesis is to describe sparse district heating conditions and explore how to improve them. Few sparse areas are heated by district heat, which reflects the economic competitiveness. A method that could be used by the district heating companies to identify the boundaries of profitable district heat is presented. Important key figures are identified when investigating the boundaries of competitive district heat. This method was identified using data gained from research on sparse areas in G\uf6teborg, Sweden and demonstrates what to focus on in order to improve competitiveness. It is concluded that distribution heat losses must decrease in future connected sparse areas to be an efficient and competitive heating alternative. The insulation properties of flexible district heating pipes, widely used when connecting sparse areas, are an important issue when improving the energy efficiency. The long term insulation properties of flexible district heating pipes are experimentally investigated by studying the cell gas transport in semi-flexible polyurethane foams. The results show that the insulation properties are impaired more rapidly than for traditional straight pipes. The flexibility of the material is partly achieved at the cost of faster gas transport. An effective diffusion barrier hindering this gas transport is thus important. A new method to determine the temperature-dependent thermal conductivity of flexible district heating pipes is presented. The method is based on the fact that the temperature decline of hot water in a district heating pipe placed in cool water depends on the thermal conductivity of the polyurethane foam. The temperature decline of the water inside the service pipe is measured and modelled numerically. The difference between measured and calculated temperatures is used to determine the temperature-dependent thermal conductivity and the specific heat by fitting. The method is based on simple measurements of the temperature decline of the service pipe water, and it is applied on single and twin pipes. A single experiment gives the thermal conductivity for a large temperature span

Sparse district heating and flexible district heating pipes

The aim of this thesis is to describe sparse district heating conditions and explore how to improve them. Few sparse areas are heated by district heat, which reflects the economic competitiveness. A method that could be used by the district heating companies to identify the boundaries of profitable district heat is presented. Important key figures are identified when investigating the boundaries of competitive district heat. This method was identified using data gained from research on sparse areas in G\uf6teborg, Sweden and demonstrates what to focus on in order to improve competitiveness. It is concluded that distribution heat losses must decrease in future connected sparse areas to be an efficient and competitive heating alternative. The insulation properties of flexible district heating pipes, widely used when connecting sparse areas, are an important issue when improving the energy efficiency. The long term insulation properties of flexible district heating pipes are experimentally investigated by studying the cell gas transport in semi-flexible polyurethane foams. The results show that the insulation properties are impaired more rapidly than for traditional straight pipes. The flexibility of the material is partly achieved at the cost of faster gas transport. An effective diffusion barrier hindering this gas transport is thus important. A new method to determine the temperature-dependent thermal conductivity of flexible district heating pipes is presented. The method is based on the fact that the temperature decline of hot water in a district heating pipe placed in cool water depends on the thermal conductivity of the polyurethane foam. The temperature decline of the water inside the service pipe is measured and modelled numerically. The difference between measured and calculated temperatures is used to determine the temperature-dependent thermal conductivity and the specific heat by fitting. The method is based on simple measurements of the temperature decline of the service pipe water, and it is applied on single and twin pipes. A single experiment gives the thermal conductivity for a large temperature span

Reasoning by Analogy - A Study on Analogy-Based Arguments in Law

This doctoral dissertation is a study on analogy-based arguments in law. Its overarching aim is to clarify reasoning by analogy in law. A model is proposed for analyzing and assessing arguments from analogy in law. The dissertation shows how analogy-based arguments in law proceed, what form they can be given and separates different steps involved in assessing whether such arguments establish the acceptability of their conclusions. It also structures the comparison of cases with respect to dimensional properties of which cases may have more or less. What reason can be given for preferring different ways of arguing from analogy in law is examined. Other central issues dealt with in the dissertation are: the relation of reasoning by analogy to past mistakes, whether arguments from analogy must be rule-based in order to be compelling, different uses of arguments from analogy in law, and the role of formal justice in normative discourse. Cases from several legal systems and areas of law exemplify reasoning by analogy, showing that this type of reasoning is not unique to a particular legal system or a particular field of law. Even though the dissertation focuses on reasoning by analogy within a legal context, much said in the dissertation of analogy-based arguments is not limited to a legal context and may thus be useful for other fields than law

Profitability of sparse district heating

The expansion of district heating into areas of low heat densities (heat sparse areas) Constitutes a challenge due to the higher distribution costs. The profitability of sparse district heating has been analysed from actual investments in 74 areas with 3227 one-family houses connected to district heating between 2000 and 2004 in Goteborg, Sweden. The profitability was estimated from a probable price model, a typical marginal heat generation cost, and the investments from the actual connections made. The analysis identified factors as the linear heat density and heat sold per house explaining the main variations in profitability. The profitability analysis was concluded with a competition analysis. The main conclusion is that sparse district heating is possible when reaching low investment costs for the local distribution network and low marginal costs for the heat generation. In Sweden, the general competitiveness of sparse district heating is facilitated by the high consumption taxes for fuel oil, natural gas, and electricity. Hence, it should be more difficult to introduce sparse district heating in other countries with low energy taxes. (c) 2008 published by Elsevier Ltd

Transient thermal conductivity of flexible district heating twin pipes

The standardized methods to measure the thermal conductivity of straight district heating pipes are not applicable on flexible district heating pipes. This paper presents a transient method determining the temperature dependent thermal conductivity of flexible twin pipes. A transient method to determine the temperaturedependent thermal conductivity of flexible single district heating pipes is presented in this paper. A flexible pipe coil is immersed into cold water. Hot water is distributed in the coil. The temperature decline of the coil water is measured and calculated. Minimizing the difference between the calculated and measured temperatures gives λ(T) of the flexible polyurethane foam. The method gives small errors