Experimental Study of a Triple Concentric Tube Heat Exchanger Integrated into a Wood-Based Air-Heating System for Energy-Efficient Dwellings

Pierre Peigné,Lionel Druette,Christian Inard

doi:10.3390/en6010184

Abstract

In this paper, experimental tests conducted on a new wood-based air-heating system for energy-efficient dwellings are presented. The main objective is to evaluate the resulting outlet temperatures and the amount of heat recovered by the ventilation air in order to assess feasibility and performance of coupling a mechanical ventilation heat-recovery unit and a triple concentric tube heat exchanger integrated into the chimney of a room-sealed wood-pellet stove to heat an entire house. After introducing the context of this work, the three main components of the combined system developed here, the coupling configuration adopted, as well as the protocol used and the sensors implemented on an experimental setup carried out in a laboratory are detailed in turn. Then, the heat transfer rates obtained from measurements for the various fluids as well as the effectiveness of the heat exchangers are presented and discussed. Finally, the resulting outlet temperatures of the three fluids exchanging in the triple concentric tube heat exchanger studied here are compared to those provided by analytical solutions obtained with a mathematical model. It is shown that heat transfer rates are predicted with a relative difference that is lower than 5% compared to experimental values and that such a system enables to cover all or most of heat losses in an energy efficient building.

Highlights

Since the building sector accounts for almost a third of final energy consumption globally and is an important source of CO2 emissions, energy efficient dwellings and their dedicated equipment are advocated by governments as suitable solutions to contribute in meeting a part of the current energy and environmental issues [1,2] while ensuring the comfort of the inhabitants
The experimental results obtained for the triple concentric tube heat exchanger (TCTHE)-NI are compared with those computed using a mathematical model [28], and the relative difference between experimental and numerical values is stated and discussed
For the sake of clarity, temperatures values as well as CO and CO2 concentrations are rounded to the nearest unit, while computed thermal powers PT pellet, PT room-sealed wood pellet stove (RSWPS) and PT flue gases (FG) are rounded to the nearest half-ten

Summary

Introduction

Since the building sector accounts for almost a third of final energy consumption globally and is an important source of CO2 emissions, energy efficient dwellings and their dedicated equipment are advocated by governments as suitable solutions to contribute in meeting a part of the current energy and environmental issues [1,2] while ensuring the comfort of the inhabitants These constructions are both highly insulated and sealed, so the fresh air needs can neither be provided by air leakage in the building envelope, nor by uncontrolled air flow rates from natural ventilation. In passive houses, remaining energy demand becomes low enough to be provided by a controlled unit at about 0.4 air changes per hour to fulfill sufficient indoor air quality conditions with no recirculated air [4] In this way, it is fundamental that all ventilation ducts are insulated and sealed against leakage. If MVHR systems can give substantial final energy reduction, the primary energy benefit depends strongly on the type of heat supply system [6]

Methods

Results

Conclusion