Pipe sizing based on domestic hot water consumption in Norwegian hotels, nursing homes, and apartment buildings

Karolina Stråby,Åse Lekang Sørensen,Harald Taxt Walnum

doi:10.1088/1757-899x/609/5/052016

Karolina Stråby, Åse Lekang Sørensen + Show 1 more

Open Access

https://doi.org/10.1088/1757-899x/609/5/052016

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Abstract

Sizing of domestic hot water pipes are to a large extent based on calculations of peak flow rate according to current guidelines. This article compares detailed field measurements of peak flow rates in Norwegian hotels, nursing homes and apartment buildings with calculated values according to Norwegian NS 3055, German DIN 1988-300 and European EN 806-3 code of practice. Results indicate that existing guidelines overestimate the peak flow rate by a factor of 1.2– 2.6, depending on type of building and which standard the calculations are based on. In most cases, this also resulted in oversizing the pipes. Calculations according to NS 3055 are closest to the field measurements, on average overestimating the peak flow rate by a factor of 1.6. To analyze the effect of different measurement intervals, the measured peak flow rate is also calculated as a moving average for different time steps (t). Compared to using an interval of 2 s, averaging the data over 10 s would underestimate the peak flow rate by a factor of 0.80– 1.0. Using a 30 s interval would underestimate the peak flow rate by 0.67– 0.94.

Highlights

As a result of an increased insulation rate and more efficient space heating systems, the energy demand for domestic hot water (DHW) is a substantial part of the total energy demand in newer buildings [1] [2]
This article compares detailed field measurements of peak flow rates in Norwegian hotels, nursing homes and apartment buildings with calculated values according to Norwegian NS 3055, German DIN 1988-300 and European EN 806-3 code of practice
Sizing of domestic hot water pipes according to Norwegian NS 3055 [6], German DIN 1988-300 [7], and European EN 806-3 [8] codes of practice are to a large extend based on calculations of peak flow rate

Summary

Introduction

As a result of an increased insulation rate and more efficient space heating systems, the energy demand for domestic hot water (DHW) is a substantial part of the total energy demand in newer buildings [1] [2]. Energy efficient DHW production and distribution systems need to i.e. maintain the desired comfort level of its' end users and the hygienic quality of the water [5]. Sizing of domestic hot water pipes according to Norwegian NS 3055 [6], German DIN 1988-300 [7], and European EN 806-3 [8] codes of practice are to a large extend based on calculations of peak flow rate. The objective of this work is to improve knowledge about peak flow rates for DHW systems by comparing calculations according to current codes of practice with field measurements. Detailed measurements of water flows and temperatures were performed on the DHW production system in each building's heating plant, for a duration of approx. Where V CCCC V CCCCCC V HHHH V HHHHHH TTCCCC TTHHHH TTHHHHHHHH TTHHHHHH is the cold water flow rate into the DHW production unit in [l/s]; is the cold water flow rate at the inlet of DHW production in [l/s]; is the hot water flow rate to the distribution system in [l/s]; is the hot water circulation flow rate in [l/s]; is the cold water temperature in [°C]; is the hot water temperature in [°C]; is the hot water production unit outlet temperature in [°C]; is the hot water circulation temperature in [°C]

Calculations

Peak flow rate

Conclusion