Experimental and analytical performance investigation of air to air two phase closed thermosyphon based heat exchangers

In recent years, the use of wickless heat pipes (thermosyphons) in heat exchangers has been on the rise, particularly in gas to gas heat recovery applications due to their reliability and the level of contingency they offer compared to conventional heat exchangers. Recent technological advances in the manufacturing processes and production of gravity assisted heat pipes (thermosyphons) have resulted in significant improvements in both quality and cost of industrial heat pipe heat exchangers. This in turn has broadened the potential for their usage in industrial waste heat recovery applications. In this paper, a tool to predict the performance of an air to air thermosyphon based heat exchanger using the ε-NTU method is explored. This tool allows the predetermination of variables such as the overall heat transfer coefficient, effectiveness, pressure drop and heat exchanger duty according to the flow characteristics and the thermosyphons configuration within the heat exchanger. The new tool's predictions were validated experimentally and a good correlation between the theoretical predictions and the experimental data, was observed. © 2014 Elsevier Ltd. All rights reserved

The performance of a heat pipe based solar PV/T roof collector and its potential contribution in district heating applications

Photovoltaic–thermal water collectors have the ability to convert solar energy into electricity and heat, simultaneously. Furthermore, the combination of photovoltaic–thermal solar collectors with a water cooling system can increase significantly the electrical and thermal efficiencies of the system, which can improve the total thermal efficiency of buildings. In this paper, the findings of six experimental configurations of solar-thermal collectors are presented and analysed. Five of the solar-thermal panel configurations were implemented with a cooling cycle. Two of the solar-thermal panels were equipped with monocrystalline silicon modules, the other two collectors were equipped with polycrystalline silicone modules, one of the collectors was based on heat pipe technology and was equipped with a cooling system, while the last collector did not include any cooling cycle. The duration of the experiments was four days during the September of 2014 and they were conducted under different solar radiation conditions. The second part of the paper presents the simulation results for five of the solar-thermal panels connected with a cooling water tank (volume of 500 litre), a domestic hot water tank (volume 350 litre) and a water-water heat pump, in terms of covering the hot water demands of a single family dwelling. The results showed that the hybrid solar collectors would be able to cover approximately 60% of the dwelling’s hot water needs for days with low levels of solar radiation, while for days with high solar radiation they could cover the hot water requirements of the family by 100%

The energy concept of the building as a part of sustainable construction

W artykule omówiono zagadnienia związane z przygotowaniem koncepcji energetycznej budynku przed etapem projektowania. Powinna ona stanowić stały element procesu realizacji budynków zrównoważonych. Autorzy wykazali potrzebę wykonywania tego typu koncepcji w kontekście idei zrównoważonego rozwoju, a także w kontekście wyzwań stawianych współczesnemu budownictwu, m.in. w zakresie efektywności energetycznej. Pokazano, że koncepcja energetyczna budynku wpisuje się dobrze w proces projektowania zintegrowanego, które zaczyna wypierać tradycyjne etapowe podejście obowiązujące dotychczas. Opisano, jakie założenia należy przyjąć przed przystąpieniem do opracowania koncepcji. Przedstawiono krótką charakterystykę wybranych systemów budynkowych mających zastosowanie w opisanych koncepcjach energetycznych. Zamieszczono dwie przykładowe koncepcje energetyczne dla budynku jednorodzinnego zeroenergetycznego, na których przykładzie dowiedziono, że korzystny bilans energetyczny można osiągnąć przy różnych założeniach dotyczących zapotrzebowania na energię użytkową do ogrzewania, różnych rozwiązaniach instalacyjnych i różnych rocznych kosztach eksploatacyjnych.In the paper the issues related to the preparation of the building’s energy concept before the design stage have been discussed. It should be a regular part of the of sustainable buildings’ implementation process. Authors demonstrated the need to perform this type of concept in the context of sustainable development as well as in the context of the challenges posed for the modern construction among others in terms of energy efficiency. It has been shown that the energy concept of the building fits well into the process of integrated design, which begins to displace the traditional phased approach in force so far. The assumptions that should be made prior to developing the concept have been described. A brief description of selected building systems, applicable in the described energy concepts, have been given. Two examples of energy concepts for zero-energy single-family building, have been described. It has been proven, that a favorable energy balance can be achieved using various assumptions concerning the demand for usable energy for heating, various installation solutions and various annual operational costs

The performance of a novel flat heat pipe based thermal and PV/T (photovoltaic and thermal systems) solar collector that can be used asan energy-active building envelope material

A novel flat heat pipe design has been developed and utilised as a building envelope and thermal solar collector with and without (PV) bonded directly to its surface. The design of the new solar collector has been validated through full scale testing in Cardiff, UK where solar/thermal, uncooled PV and PV/T tests were carried out on three identical systems, simultaneously. The tests showed a solar/thermal energy conversion efficiency of around 64% for the collector with no PV and 50% for the system with the PV layer on it. The effect of cooling on the solar/electrical energy conversion efficiency was also investigated and an efficiency increase of about 15% was recorded for the cooled PV system due to the provided homogenous cooling. The new flat heat pipe solar collector is given the name "heat mat" and, in addition to being an efficient solar collector type, it is also designed to convert a building envelope materials to become energy-active. A full size roof that utilise this new building envelope material is reported in this paper to demonstrate the way this new collector is integrated as a building envelope material to form a roof. A thermal absorption test, in a controlled environment, from the ambient to the heat mat with no solar radiation is also reported. The test has proved the heat mat as an efficient thermal absorber from the ambient to the intermediate fluid that deliver the heat energy to the heat pump system.The work has been funded by DECC under contract number EEF371