Faculty of Mechanical Engineering Institute of Power Engineering

Faculty of Mechanical Engineering Institute of Power Engineering, Professorship of Energy System Engineering and Heat Economy Adapted control systems for house service connection stations of huge performance – domestic hot water supply based on continuous flow system Dipl. -Ing. Norbert Wünsche, Dr. -Ing. Karin Rühling TU Dresden, Institut of Power Engineering This presentation is based on a research project financially supported by the German Federal Ministry of Economy within the PROgramm “INNOvationskompetenz mittelständischer Unternehmen” (KF 0100804 KMH 3) Second Euroheat & Power RTD Workshop Brussels, 2 -3 February 2006

MOTIVATION Domestic hot water supply in the range of 100 k. W to 1 MW § Standard installations temporary mostly as storage systems favourable conditions for growth of Legionella Brussels, 2 February 2006 Huge DHW supply based on continuous flow system Wünsche/Rühling Storage of DHW Storage charging system Storage of DHW Storage system § Cause of high quality standards (Trinkw. V, DVGW W 551) special solutions with considerable high efforts necessary 2

OBJEKTIVE Check, if continuous flow system can be applied primary storage for heating water § domestic hot water temperature control system based on speed control of electronic pumps Without storage Brussels, 2 February 2006 Huge DHW supply based on continuous flow system Wünsche/Rühling Storage of heating water § Continuous flow system with primary storage simple hydraulic circuit Continuous flow system § 3

Tested basic configurations on DHW side DHW supply primary storage of heating water circulation return DW Two-stage principle – during tapping treturn , as no mixing circulation/cold DW Brussels, 2 February 2006 Huge DHW supply based on continuous flow system Wünsche/Rühling 4

Two-point control Thermo mechanical valve Control system without auxiliary power demand Brussels, 2 February 2006 Huge DHW supply based on continuous flow system Wünsche/Rühling Motor control valve indirect charging Motor control valve Three-point control Basic configurations for charging the primary storage Adjusted charging temperature 5

Choice of the pump Brussels, 2 February 2006 Huge DHW supply based on continuous flow system Wünsche/Rühling 6

Set-up of the laboratory test facility temp. HX inlet temp. DHW with sensor head trans -mitter § Single-stage realisation § Qth, design = f(tstorage) = 100 … 150 k. W § Switching the mixing valve via flow control switch 0. . 12 l/min t. HX, in=65 °C temp. circ. return temp. HX outlet SIKA flow control switch Brussels, 2 February 2006 temp. DW nonreturn valve > 12 l/min t. HX, in= tstorage § Control pump Grundfos TPE 25 -90 R (smallest available) § Plate HX SWEP B 28 x 30 § Rudert DW-storage 200 l Huge DHW supply based on continuous flow system Wünsche/Rühling 7

Key aspects of the laboratory tests § Test of different hydraulic circuits § Measuring the time constants of different temperature sensors § Placement of DW-temperature sensor in heat exchanger § Examination of the control range of the electronic pump § Dimensioning the admix-quantity § Choice of proper mixing valve § Choice of appropriate flow control switch § Optimisation of pump control parameters Brussels, 2 February 2006 Huge DHW supply based on continuous flow system Wünsche/Rühling 8

Selected results of the laboratory tests with 72 °C storage temperature Load profile Step curve Load profile Jump function Brussels, 2 February 2006 Huge DHW supply based on continuous flow system Wünsche/Rühling 9

Selected results of the laboratory tests Maximum values Minimum values average positive deviation average negative deviation Load function / storage temperature Step curve 72 °C +2, 2 K -3, 6 K +0, 3 K -1, 2 K Jump function 72 °C +5, 5 K -3, 6 K +0, 7 K -1, 1 K Step curve 80 °C +2, 1 K -1, 9 K +0, 2 K -0, 4 K Jump function 80 °C +6, 5 K -5, 7 K +0, 5 K -0, 7 K Brussels, 2 February 2006 Huge DHW supply based on continuous flow system Wünsche/Rühling 10

Field test – Objectives Prove under praxis conditions § uninterrupted service, § dimensioning of performance, § stability of control, § effectiveness of primary storage (coverage of peak demands) as well as § low return flow temperatures and thus Single-stage realisation Brussels, 2 February 2006 § function of complete system Huge DHW supply based on continuous flow system Wünsche/Rühling 11

Field test – Conditions of application For 53 living units § two-stage DW-heating § first operation period single-stage and later two-stage operation § mixing loop as independent temperature control circuit § no cold water flow sensor § data logging 11 temperature sensors 3 flow rate sensors average value logging (2 or 5 s–pulse) 8 weeks save and convenient supply of tenants V´DHW, max = 2, 95 m³/h (Comparison: DIN 4708 4, 8 m³/h) Brussels, 2 February 2006 Huge DHW supply based on continuous flow system Wünsche/Rühling 12

Field test - Selected results – Daily average values Remarkable higher control stability in the two-stage realisation (± 2 K) Brussels, 2 February 2006 Huge DHW supply based on continuous flow system Wünsche/Rühling 13

Field test - Selected results – Daily course; two-stage Brussels, 2 February 2006 Huge DHW supply based on continuous flow system Wünsche/Rühling 14

Field test - Selected results – Peak demand; two-stage Brussels, 2 February 2006 Huge DHW supply based on continuous flow system Wünsche/Rühling 15

flow rate in m 3/h Field test - Selected results – Frequency distribution DHW demand frequency distribution flow rate of area-equivalent rectangle: 0, 134 m 3/h time in % § DHW-demand only 32 % of the time § only during 10 % of the time demand > 0, 5 m³/h § dimensioning of primary storage = f (circulation demand, operation parameter of heat exchanger, mixing loop, storage temperature. . ) program for dimensioning Brussels, 2 February 2006 Huge DHW supply based on continuous flow system Wünsche/Rühling 16