... that Mastercool MMB10 cooler has a much higher cooling capacity
with outdoor vs mixed indoor and outdoor air, which cuts the net output
way down from 69K to 3K Btu/h...

Oops. That only applies on planets where 100 Btu can evaporate
a pound of water (Abby, aren't you checking all this? :-) On earth,
it looks like it can deliver 30.4K Btu/h, with a remote exhaust fan...

20 TAS=110'spec outdoor temp (F)
30 RHS=10'spec outdoor RH (%)
40 DTS=32'spec temp diff (F)
50 PAO=RHS/100*EXP(17.863-9621/(460+TAS))'spec outdoor vapor pressure ("Hg)
60 PWO=EXP(17.863-9621/(460+(TAS-DTS)))'spec cooler vapor pressure ("Hg)
70 CS=2000'spec cfm
80 PS=DTS*CS*1.08/1000'spec water evaporation rate (lb/h)
90 WO=.62198/(29.921/PAO-1)'spec outdoor humidity ratio
100 TI=80'indoor temp setpoint (F)
110 PWI=EXP(17.863-9621/(460+TI))'indoor cooler vapor pressure ("Hg)
120 WI=.012'indoor humidity ratio setpoint
130 PAI=29.921/(1+.62198/WI)'cooler air vapor pressure ("Hg)
140 P=PS*(PWI-PAI)/(PWO-PAO)'indoor water evaporation rate (lb/h)
150 C=P/(4.5*(WI-WO))'outdoor airflow with remote exhaust (cfm)
160 Q=1000*P-(90-80)*C'sensible cooling with Ta = 90 F (Btu/h)
170 PRINT C,P,Q

ext airflow water cooling
(cfm) (lb/h) (Btu/h)

1622.744 46.65193 30424.49

And a box and an intake window fan can increase the cooling 23%...

140 PIND=PS*(PWI-PAI)/(PWO-PAO)'indoor evaporation rate (lb/h)
150 PSWP=PS*(PWI-PAO)/(PWO-PAO)'swamp evaporation rate (lb/h)
160 PRINT PS,PIND,PSWP
170 C=2000'outdoor airflow with local intake (cfm)
180 P=4.5*C*(WI-WO)'average evaporation rate (lb/h)
190 Q=1000*P-(90-80)*C'sensible cooling with Ta = 90 F (Btu/h)
200 F=(P-PIND)/(PSWP-PIND)'swamp fraction
210 PRINT C,P,Q,F

water evaporation rates (lb/h)
spec indoor swamp

69.12 46.65193 75.62949

ext airflow water cooling swamp
(cfm) (avg lb/h) (Btu/h) fraction

2000 57.4976 37497.6 .3742781

For more cooling capacity with dry outdoor air, we might put one near
a window inside a house with a $55 Lasko 2155A 16" 90 W 2470 cfm intake
fan in the window and use the fan thermostat to turn on the cooler when
the room temp rises to 80 F and a humidistat to turn on the fan when
the indoor RH rises to 56%, with 1-way plastic film dampers in a box
between the cooler and the window to force outdoor fan air to flow
through the cooler pad when the window fan is running and make indoor
air flow through the cooler when the window fan is not running, like
this, viewed in a fixed font like Courier:

| |
| |
---------
| |llld| |
|c| d| | outdoors
|o| d|f|
2K cfm ==|o| d|a| == 2K cfm With the window fan off, indoor air
|l| d|n| would flow in through left and right
|e| d| | dampers lll and rrr. With the fan on,
|r| d| | ddd would open and the fan air would
| |rrrd| | force lll and rrr closed.
---------
| |

80 F 56%| window fan cooler fan cooler water
--------------|-----------------------------------------------
1. no no | off off off
2. no yes | on off off dehum
3. yes no | off on on indoor
4. yes yes | on off on swamp

Case 3 would maintain indoor comfort with less water than an external
swamp cooler, for a house with significant natural air leakage, ie
for almost all houses.

Nick