INVESTIGATION OF THE UNCERTAINTY VALUE AT MEASURING THE TEMPERATURE OF THE COOLANT IN THE PIPELINES WITH OUTSIDE SURFACE MOUNTED TEMPERATURE SENSORS

Abstract

During performing technological and production processes and monitoring the modes of their operation, the problem of determining the temperature of various media transported through pipelines is solved without incut temperature sensors (TS) in them, i.e. with using outside surface mounted TS (SMTS). This method is allowing to measure mechanical values at technological processes without structure broken and without influence to physicochemical properties of measured media.
 Using of SMTS possible to register heat losses on sections of heating mains, pollution degree of pipelines internal walls, to control serviceability of measurement channels of temperature of the coolant in heat meters, etc.
 In the article authors presents results of research the uncertainty values for measuring of the coolant temperature in heating systems pipelines under different modes of its flow. First of all, the uncertainty value of the measurements results was estimated, which was determined by the results of the study for the calculation model and field tests at existing district heating systems.
 Emphasis is paid on estimating the difference between the registration of temperature in the middle of the pipeline, determined by mortise transducers and the temperature measured by outside surface mounted temperature transducers, taking into account the temperature gradient across the pipeline and the quality of its insulation.
 It is determined that: the temperature measured by temperature transducers on the surface of the pipeline at different points of its perimeter, with proper installation and sufficient thermal insulation does not depend on their location; the average temperature on the surface of the pipeline, measured using the developed method of installation of PT, slightly differs (ΔT ≈- 0.3⁰C) from the average temperature of the coolant in the middle of the flow; temperature transducers have high reproducibility of measurements and small difference in readings between channels at parallel measurements (»0,03⁰С).
 It is substantiated that high metrological performances of temperature transducers allow to use them for solving other tasks: measuring the distribution of heat fluxes in heating systems of residential buildings to perform hydraulic balancing of heating systems and increase their efficiency; estimate of contamination of pipelines and heat exchange equipment to determine the need for their washing; determination of thermal resistance of buildings protective structures to assess their energy efficiency; determination of large pumps efficiency by calorimetric method; checking the correct of operation the temperature measuring channels of heat meters and cold meters; in other technology areas where measurements of small temperature differences with high accuracy are required.