Effeciency testing

The given test scenario describes and investigates how much the COP of a heat pump system can be improved by implementing thermal stratification. The tests have been performed at EyeCular Technologies’ laboratory.

Test equipment

The test facility is equipped with 24 temperature sensors (thermocouples), positioned with a vertical distance of 50mm figure 9. Temperatures are logged every 10 second by a data logger (Agilent 34972A LXI).

Test setup

There are two test setups. The tests will be performed separately, but performed with the same starting and operating conditions. This will ensure comparable test results, and enable quantification of the difference between the COPs of the two given system designs.

Setup 1:

Standard fixed connection placed in a vertical height of 800mm.

Setup 2:

StratiFlex™ is integrated through the bottom of the storage tank.

Starting conditions:                               Flow conditions:

·  Top 1/3 volume:    55 ⁰C                                   ·  17.5 l/min

·  Middle 1/3 volume: 35 ⁰C                                  ·  Circulation our from the bottom of tank

·  Bottom 1/3 volume: 15 ⁰C                                 ·  6 cycles of ∆T = 7 K

Test Results

Below, on Figure 1 and Figure 2, the results of the two test setups are shown.

 

Each of the colored lines represent a reading of one of the 24 temperature sensors in the tank. The black line represents the inlet temperature to the tank. The y-axis is temperature in degree Celsius, and the x-axis is the volume of circulated water in liters.

Comparison

There is a great difference in both the top and bottom temperatures of the two comparison tests.

In Setup 1

The inlet water is being mixed with the water in the tank, mainly because of jet mixing. But plume entrainment will also occur, since the fixed inlet can result in warm water being positioned below colder water, in this case in the beginning of the test. As some of the hot zone is mixed into the lower grade layers of water, the average operating temperature for the heat pump is higher throughout the entire duration of the test, compared to setup 2.

In Setup 2

Thermally stratified by StratiFlex™. The bottom temperatures are kept almost as cold as possible throughout the entire test duration, ensuring the most optimal operating conditions for the heat pump. Plume entrainment is greatly reduced as StratiFlex™ is always positioning the inlet water in the appropriate thermal layer, and jet mixing is also greatly reduced as StratiFlex™ reduces the inlet water velocity to the recommendable range of velocity.