Design of a Rapid Beverage Chiller

for iced tea enthusiasts

Unaided, iced tea takes hours to make

Brew: 2-8 minutes Cool: 2-6 hours

Market for specialized kitchen tools

Brew directly into iceFunctionality:• Fill pitcher with ice• Brews tea• Pours tea into pitcher

Issues:• Hot tea melts ice• Ice dilutes tea• “That freezer taste”

Ice water circulationFunctionality:• Add ice and water• Insert can or bottle• Rotates container, sprays

with ice water

Issues:• Requires ice (minor)• Bad for tea (fixable?)

Cool new technology: TEC’s

Pros:• Super compact, light• No moving parts

Cons:• Inefficient (40-70%)

(≈300% for full-size fridge)

Ice versus price

Isolated-ice systems

Pros:• More inexpensive• Likely more compact

Cons:• Needs lots of ice for hot tea

Proposal: TEC-cooled system

Pros:• Plug and play• Precise temperatures

Cons:• Pricier• Bulky (heatsinks!)• Draws a lot of power• Gives off a lot of heat

Rapid Beverage Cooler: Take 1

Vessel + sensor

Heatsink Fan

Stirrer

Spigot

TEC

Design 1: Too hot for TEC operation!

Problem:• Can’t operate past ≈80°C• Not needed at high temps

Solution:• Only run TEC below

certain temperature

Rapid Beverage Cooler: Take 2 Three-state process:

1. Upper fans on, TEC off: Cool to ≈60°C

2. All fans on, TEC on: Cool to room temp.

3. Lower fans on, TEC on: Cool to final temp.

Circuit breaker limits performance• Power from wall: 1500 W (US/Canada)• Power through TEC(s): 1200 W• Breaker is limiting factor (67% efficient TEC):

0.67 × 1500 W × 0.8 = 800 W

Calculate the temperature profile:• Aggressive air cooling• Constant TEC heat flow: 800W (simplistic)• TEC turns on at 60°C

Cool a liter of tea in 9 minutes

2 4 6 8 10

20

40

60

80

100

Time elapsed (minutes)

Tem

pera

ture

(°C)

Problems I may encounter…• Variation in TEC heat transfer rate– Stage 2: Better than estimated– Stage 3: Worse than estimated

• Heat dissipation too slow

→ Slower cooling process.

• Too expensive to mass-produce (>$250?) Backup plan: Investigate other cooling systems

• Demand for iced tea chillers

• TECs enable powerful, convenient chillers

• 1 liter: 90°C to 6°C in 9 minutes