Hi Guys

I am currently calculating plant design for the refurb of an Altitude Test Chamber.
Chamber Spec is 150 degC to -60 degC. With Humidity control and Vacuum control.
We will be using a Jumo Imago 500 for temp, Hum and vacuum control.
Cooling done by refrigeration. Heating by elec heaters. Humidity by water spray, de-hum by HT de-hum coil refrigeration. Vacuum by Vacuum pump.

We will be using a cascade plant HT R404a and LT R23.

I have calculated the evap LT at -60 deg C 10.4 kw Tubed evap, no fins
Condensing LT @ -10 deg C ?
LT compressor Bitzer 4 CC 6.2

I the calculated the evap HT @ -15 deg C 20.58kw
Cond HT @ 40 deg C 31.9 kw heat rejection
Using a plate heat exchanger and calculated a flow rate of 1.547 l/sec with a 5 deg TD
HT compressor Bitzer 4 PC 15.2

I have seized the cascade condenser electric stepper valve from carel to E2V - 30.
Still awaiting Carel On R23 specifications. Valves, transducers ect.

I will be using Hot gas by-pass and liq injection to both stages for comp control.
I will be using a CPR for LT stage for pull down from high temp. Will set between 40 - 60 psi


My question is?

How do I calculate the Expansion tank?
How do I calculate the blow of valve?
is my -10 degC LT R23 Condensing optimum? was reading up and some say between -10 to -20 degC?
How do I calculate the captube for equalization between Hp and Lp of the LT system?
How do I calculate the captube between suction and expansion tank?

I would appreciate your advice a lot.