Westinghouse Electric Corp.'s third-quarter profits from operations fell from their level of a year earlier, but two transactions helped the company's net income climb 8.7 percent on a slim 1.8 percent sales gain.

Third-quarter net income rose to $113.7 million ($1.31 a share) from $104.6 million ($1.21) a year earlier. Sales edged up to $2.32 billion from $2.28 billion. Nine-month net income rose 4 percent to $348.5 million ($4.03) from $334.9 million ($3.90) in the comparable 1981 period. Sales climbed to $7.13 billion from $6.84 billion.

The special transactions helping increase net income were the sale of Westinghouse Broadcasting and Cable's 50 percent interest in Showtime, a pay-television service, for $75 million, which generated a per-share gain of 16 cents, and Westinghouse's agreement to buy $58 million of two of its debt issues, resulting in a gain of 11 cents a share.

Kaiser Aluminum & Chemical Corp. had an operating loss of $107.3 million in the third quarter, but it was offset by a pretax gain of $180.6 million from an amendment to a natural gas supply contract with Texaco Inc. for Kaiser's Louisiana aluminum plant.

As a result, Kaiser reported yesterday that net income was $63.3 million ($1.46 a share) in the quarter on revenues of $895.6 million compared with net income in the 1981 third quarter of $12.3 million (28 cents) on revenues of $794.3 million. Sales slipped to $696.3 million from $780 million.

Nine-month profits were $8.4 million (18 cents) on revenues of $2.245 billion compared with 1981 nine-month profits of $148.9 million ($3.46) on revenues of $2.508 billion.

Kaiser Chairman Cornell C. Maier said the most significant portion of the third-quarter results was the continued operating loss in the aluminum business. It was the fourth consecutive quarter of losses for that operation.

Whirlpool Corp. said yesterday that third-quarter sales and earnings were down nearly 10 percent and cited the recession.

The manufacturer of household appliances said sales were $609.8 million, down 9 percent from $670.4 million a year ago. Net earnings were $36.7 million, down 9.6 percent from $40.6 million a year ago, said Whirlpool Chairman John H. Platts.

So far this year, Whirlpool sales have been $1.83 billion compared with $2.02 billion for the first nine months of 1981. Net earnings are $101.1 million, down from $108.3 million for the first nine months of 1981.