Methodology for identifying parameters for the TRNSYS model Type 210 -wood pellet stoves and boilers

This report describes a method how to perform measurements on boilers and stoves and how to identify parameters from the measurements for the boiler/stove-model TRNSYS Type 210. The model can be used for detailed annual system simulations using TRNSYS. Experience from measurements on three different pellet stoves and four boilers were used to develop this methodology. Recommendations for the set up of measurements are given and the re-quired combustion theory for the data evaluation and data preparation are given. The data evalua-tion showed that the uncertainties are quite large for the measured flue gas flow rate and for boilers and stoves with high fraction of energy going to the water jacket also the calculated heat rate to the room may have large uncertainties. A methodology for the parameter identification process and identified parameters for two different stoves and three boilers are given. Finally the identified models are compared with measured data showing that the model generally agreed well with meas-ured data during both stationary and dynamic conditions.

Characterization of residential chimney conditions for flue gas flow measurements

A literature survey and a theoretical study were performed to characterize residential chimney conditions for flue gas flow measurements. The focus is on Pitot-static probes to give sufficient basis for the development and calibration of a velocity pressure averaging probe suitable for the continuous dynamic (i.e. non steady state) measurement of the low flow velocities present in residential chimneys. The flow conditions do not meet the requirements set in ISO 10780 and ISO 3966 for Pitot-static probe measurements, and the methods and their uncertainties are not valid. The flow velocities in residential chimneys from a heating boiler under normal operating condi-tions are shown to be so low that they in some conditions result in voiding the assumptions of non-viscous fluid justifying the use of the quadratic Bernoulli equation. A non-linear Reynolds number dependent calibration coefficient that is correcting for the viscous effects is needed to avoid significant measurement errors. The wide range of flow velocity during normal boiler operation also results in the flow type changing from laminar, across the laminar to turbulent transition region, to fully turbulent flow, resulting in significant changes of the velocity profile during dynamic measurements. In addition, the short duct lengths (and changes of flow direction and duct shape) used in practice are shown to result in that the measurements are done in the hydrodynamic entrance region where the flow velocity profiles most likely are neither symmetrical nor fully developed. A measurement method insensitive to velocity profile changes is thus needed, if the flow velocity profile cannot otherwise be determined or predicted with reasonable accuracy for the whole measurement range. Because of particulate matter and condensing fluids in the flue gas it is beneficial if the probe can be constructed so that it can easily be taken out for cleaning, and equipped with a locking mechanism to always ensure the same alignment in the duct without affecting the calibration. The literature implies that there may be a significant time lag in the measurements of low flow rates due to viscous effects in the internal impact pressure passages of Pitot probes, and the significance in the discussed application should be studied experimentally. The measured differential pressures from Pitot-static probes in residential chimney flows are so low that the calibration and given uncertainties of commercially available pressure transducers are not adequate. The pressure transducers should be calibrated specifically for the application, preferably in combination with the probe, and the significance of all different error sources should be investigated carefully. Care should be taken also with the temperature measurement, e.g. with averaging of several sensors, as significant temperature gradients may be present in flue gas ducts.

Flexibilitetens frammarsch, en studie om den intermittenta anställningen

Flexible working conditions is used extensively in organizations today as a way to create flexibility for the employer. Recently we’ve been reading in the newspapers that this approach is a growing problem and the EU has warned Sweden twice that abuse of these forms of employment must be stopped. The Government has recently submitted a proposed rule change to reduce the possibility of stacking one temporary contract after another. Borlänge kommun makes themselves more flexible with the intermittent employments. This study aims to examine why infrequent employments, such as the intermittent employment is used and preferred by Borlänge kommun and how it’s perceived by affected employees in the organization. The questions related, besides why the intermittent employment is used by the organization and how its perceived by those involved, also includes the management of intermittent employment and how the organization is handling work contracts. The background information on the employment law implications gives the reader an insight into how the regulatory framework works surrounding the topic. The theory section highlights the main theories about flexibility and its different shapes and perspectives. For the study a qualitative approach is used. A case study with semi-structured interviews was performed. The respondents were employees involved in the staffing of intermittent employees and also members of the staff with an intermittent employment. The results show that the employment and contracts is correctly handled by labour law regulations. This study shows that Borlänge kommun uses intermittent employments extensively, with its 1 320 intermittently employees. If this is abuse, or not, is not clear from the result. The authors discuss, however, if that is the case. The intermittent employment is used mainly because of the great needs. This is because society is changing and the average age is increasing, both by those using the services and the employees. All respondents perceive the intermittent employment as most flexible for the employees. Respondents working in the staffing department say that they are not flexible enough. The intermittent employees’ working today does not cover the great need. Borlänge kommun think that the flexibility should benefit them more and is currently trying to become more flexible. The employees were generally satisfied with their work situation. Some tendencies of insecurity and uncertainty could be inferred from the intermittent employees answers. The author’s conclusions are that flexibility and the intermittent employment contracts mainly benefit the employer and the employees who actively choose this type of work, such as students. This kind of employment affects, however, the society and those who need a secure lifestyle. The necessary permanent contracts are becoming fewer and replaced by precarious and flexible employment conditions.