I have few happy thoughts to share after testing my gadget, and mainly they are about success at air-cooling method that I did use.
ZS-PD9 with 12V as input and by this having an 24V output at 4A load and 8A consumption from the source (that is close 10A max), this managed to stay at 32C.
These news translates that I can use entire 160W Max of it potentials with out fear that this will be in flames.
Buck Voltage Converter this is a rough way of boosting or step down energy.
Noise level of produced DC this simile to orchestra of Asian drums, practically Buck Voltage Converter they can happily cooperate in applications in which another power supply will use their energy and feed it to the load.
For example specific module this is designed to serve mainly to voltage conversion of cars voltages.
12 -> 24
Other applications for it they are much rare, as for example 24V ->36 or 24V -> 48V
In such rare applications it is expected temperature of the module to raise much higher than when this works at 12V->24, my tests shown to me that at such condition even with out active cooling temperature never gets at dangerous limits for the health of active components (70 Celsius).
In an older experiment of my in which I did try to use ZS-PD9 as charger for the battery of my electric bicycle, by setting output voltage to 42V with input of 24V 10A, heat sink it did become extremely hot.
At this configuration I was wasting 240W of incoming energy and I was getting 42V and almost 3.2A ( about 150W ), therefore 100W were loses them converted in to heat.
In conclusion any Buck Voltage Converter this does boost or step-down more than 12V from the source voltage, this eventually it will heat up allot.
Many kids buying from eBay cheap Buck converter with LCD screen so this to be used as laboratory power supply, but what they are not aware of, this is how much actual power in watts this gets wasted by such cheap Buck converter when this turning in to heat.
Finally when you do use cheap Buck converter and you do not own a real oscilloscope, your are much happier.
Rough energy conversion of Buck converter, this can not be truly filtered even if you do add a huge in capacity electrolytic capacitor of 15000uF and current this be just of few Amperes.
DC voltage loaded with parasitic frequencies, it could cause issues if you do try to power with it a portable TV (24V) from a 12V battery.
Therefore to sum up, Buck converters they suffer from thermal losses when they multiply or divide source voltage more than two times (2X).
DC voltage loaded with parasitic frequencies it can power incandescent light bulbs or LED, or we can use this energy for power conversion purposes.
But personally I would not trust one cheap Buck converter this to charge my costly laptop at 19V.
My personal use of ZS-PD9 this will be for testing electrolytic capacitors up to 60V (63V) specification, my own (quality made) laboratory DC power supply can go up to 35V.
Therefore one Buck converter of few Euros worth, it did saved my day.